From eb352a5f6bdb48cb2d795e3fe2cd7d354580a761 Mon Sep 17 00:00:00 2001
From: Neil Alexander <neilalexander@users.noreply.github.com>
Date: Fri, 4 Feb 2022 10:39:34 +0000
Subject: [PATCH] Full roomserver input transactional isolation (#2141)

* Add transaction to all database tables in roomserver, rename latest events updater to room updater, use room updater for all RS input

* Better transaction management

* Tweak order

* Handle cases where the room does not exist

* Other fixes

* More tweaks

* Fill some gaps

* Fill in the gaps

* good lord it gets worse

* Don't roll back transactions when events rejected

* Pass through errors properly

* Fix bugs

* Fix incorrect error check

* Don't panic on nil txns

* Tweaks

* Hopefully fix panics for good in SQLite this time

* Fix rollback

* Minor bug fixes with latest event updater

* Some review comments

* Revert "Some review comments"

This reverts commit 0caf8cf53e62c33f7b83c52e9df1d963871f751e.

* Fix a couple of bugs

* Clearer commit and rollback results

* Remove unnecessary prepares
---
 roomserver/internal/helpers/auth.go           |  13 +-
 roomserver/internal/input/input.go            |  57 +++-
 roomserver/internal/input/input_events.go     |  84 +++---
 .../internal/input/input_latest_events.go     |  18 +-
 roomserver/internal/input/input_membership.go |   4 +-
 roomserver/internal/input/input_missing.go    |  12 +-
 roomserver/state/state.go                     |  17 +-
 roomserver/storage/interface.go               |   7 +-
 .../storage/postgres/event_json_table.go      |   5 +-
 .../postgres/event_state_keys_table.go        |  10 +-
 .../storage/postgres/event_types_table.go     |   5 +-
 roomserver/storage/postgres/events_table.go   |  30 +-
 roomserver/storage/postgres/invite_table.go   |  13 +-
 .../storage/postgres/membership_table.go      |  67 +++--
 .../storage/postgres/published_table.go       |  10 +-
 .../storage/postgres/room_aliases_table.go    |  15 +-
 roomserver/storage/postgres/rooms_table.go    |  27 +-
 .../storage/postgres/state_block_table.go     |  11 +-
 .../storage/postgres/state_snapshot_table.go  |   5 +-
 .../storage/shared/latest_events_updater.go   | 133 ---------
 roomserver/storage/shared/room_updater.go     | 262 +++++++++++++++++
 roomserver/storage/shared/storage.go          | 273 +++++++++++-------
 .../storage/sqlite3/event_json_table.go       |  11 +-
 .../storage/sqlite3/event_state_keys_table.go |  21 +-
 .../storage/sqlite3/event_types_table.go      |   5 +-
 roomserver/storage/sqlite3/events_table.go    |  19 +-
 roomserver/storage/sqlite3/invite_table.go    |  13 +-
 .../storage/sqlite3/membership_table.go       |  45 ++-
 roomserver/storage/sqlite3/published_table.go |  10 +-
 .../storage/sqlite3/room_aliases_table.go     |  15 +-
 roomserver/storage/sqlite3/rooms_table.go     |  33 ++-
 .../storage/sqlite3/state_block_table.go      |   9 +-
 .../storage/sqlite3/state_snapshot_table.go   |   3 +-
 roomserver/storage/sqlite3/storage.go         |  42 +--
 roomserver/storage/tables/interface.go        |  62 ++--
 35 files changed, 867 insertions(+), 499 deletions(-)
 delete mode 100644 roomserver/storage/shared/latest_events_updater.go
 create mode 100644 roomserver/storage/shared/room_updater.go

diff --git a/roomserver/internal/helpers/auth.go b/roomserver/internal/helpers/auth.go
index ddda8081c..9af0bf591 100644
--- a/roomserver/internal/helpers/auth.go
+++ b/roomserver/internal/helpers/auth.go
@@ -20,17 +20,22 @@ import (
 	"sort"
 
 	"github.com/matrix-org/dendrite/roomserver/state"
-	"github.com/matrix-org/dendrite/roomserver/storage"
 	"github.com/matrix-org/dendrite/roomserver/types"
 	"github.com/matrix-org/gomatrixserverlib"
 )
 
+type checkForAuthAndSoftFailStorage interface {
+	state.StateResolutionStorage
+	StateEntriesForEventIDs(ctx context.Context, eventIDs []string) ([]types.StateEntry, error)
+	RoomInfo(ctx context.Context, roomID string) (*types.RoomInfo, error)
+}
+
 // CheckForSoftFail returns true if the event should be soft-failed
 // and false otherwise. The return error value should be checked before
 // the soft-fail bool.
 func CheckForSoftFail(
 	ctx context.Context,
-	db storage.Database,
+	db checkForAuthAndSoftFailStorage,
 	event *gomatrixserverlib.HeaderedEvent,
 	stateEventIDs []string,
 ) (bool, error) {
@@ -92,7 +97,7 @@ func CheckForSoftFail(
 // Returns the numeric IDs for the auth events.
 func CheckAuthEvents(
 	ctx context.Context,
-	db storage.Database,
+	db checkForAuthAndSoftFailStorage,
 	event *gomatrixserverlib.HeaderedEvent,
 	authEventIDs []string,
 ) ([]types.EventNID, error) {
@@ -193,7 +198,7 @@ func (ae *authEvents) lookupEvent(typeNID types.EventTypeNID, stateKey string) *
 // loadAuthEvents loads the events needed for authentication from the supplied room state.
 func loadAuthEvents(
 	ctx context.Context,
-	db storage.Database,
+	db state.StateResolutionStorage,
 	needed gomatrixserverlib.StateNeeded,
 	state []types.StateEntry,
 ) (result authEvents, err error) {
diff --git a/roomserver/internal/input/input.go b/roomserver/internal/input/input.go
index 7834e2edc..5bdec0a24 100644
--- a/roomserver/internal/input/input.go
+++ b/roomserver/internal/input/input.go
@@ -19,6 +19,7 @@ import (
 	"context"
 	"encoding/json"
 	"errors"
+	"fmt"
 	"sync"
 	"time"
 
@@ -38,6 +39,19 @@ import (
 	"github.com/tidwall/gjson"
 )
 
+type retryAction int
+type commitAction int
+
+const (
+	doNotRetry retryAction = iota
+	retryLater
+)
+
+const (
+	commitTransaction commitAction = iota
+	rollbackTransaction
+)
+
 var keyContentFields = map[string]string{
 	"m.room.join_rules":         "join_rule",
 	"m.room.history_visibility": "history_visibility",
@@ -101,7 +115,8 @@ func (r *Inputer) Start() error {
 				_ = msg.InProgress() // resets the acknowledgement wait timer
 				defer eventsInProgress.Delete(index)
 				defer roomserverInputBackpressure.With(prometheus.Labels{"room_id": roomID}).Dec()
-				if err := r.processRoomEvent(context.Background(), &inputRoomEvent); err != nil {
+				action, err := r.processRoomEventUsingUpdater(context.Background(), roomID, &inputRoomEvent)
+				if err != nil {
 					if !errors.Is(err, context.DeadlineExceeded) && !errors.Is(err, context.Canceled) {
 						sentry.CaptureException(err)
 					}
@@ -111,7 +126,12 @@ func (r *Inputer) Start() error {
 						"type":     inputRoomEvent.Event.Type(),
 					}).Warn("Roomserver failed to process async event")
 				}
-				_ = msg.Ack()
+				switch action {
+				case retryLater:
+					_ = msg.Nak()
+				case doNotRetry:
+					_ = msg.Ack()
+				}
 			})
 		},
 		// NATS wants to acknowledge automatically by default when the message is
@@ -131,6 +151,37 @@ func (r *Inputer) Start() error {
 	return err
 }
 
+// processRoomEventUsingUpdater opens up a room updater and tries to
+// process the event. It returns whether or not we should positively
+// or negatively acknowledge the event (i.e. for NATS) and an error
+// if it occurred.
+func (r *Inputer) processRoomEventUsingUpdater(
+	ctx context.Context,
+	roomID string,
+	inputRoomEvent *api.InputRoomEvent,
+) (retryAction, error) {
+	roomInfo, err := r.DB.RoomInfo(ctx, roomID)
+	if err != nil {
+		return doNotRetry, fmt.Errorf("r.DB.RoomInfo: %w", err)
+	}
+	updater, err := r.DB.GetRoomUpdater(ctx, roomInfo)
+	if err != nil {
+		return retryLater, fmt.Errorf("r.DB.GetRoomUpdater: %w", err)
+	}
+	action, err := r.processRoomEvent(ctx, updater, inputRoomEvent)
+	switch action {
+	case commitTransaction:
+		if cerr := updater.Commit(); cerr != nil {
+			return retryLater, fmt.Errorf("updater.Commit: %w", cerr)
+		}
+	case rollbackTransaction:
+		if rerr := updater.Rollback(); rerr != nil {
+			return retryLater, fmt.Errorf("updater.Rollback: %w", rerr)
+		}
+	}
+	return doNotRetry, err
+}
+
 // InputRoomEvents implements api.RoomserverInternalAPI
 func (r *Inputer) InputRoomEvents(
 	ctx context.Context,
@@ -177,7 +228,7 @@ func (r *Inputer) InputRoomEvents(
 			worker.Act(nil, func() {
 				defer eventsInProgress.Delete(index)
 				defer roomserverInputBackpressure.With(prometheus.Labels{"room_id": roomID}).Dec()
-				err := r.processRoomEvent(ctx, &inputRoomEvent)
+				_, err := r.processRoomEventUsingUpdater(ctx, roomID, &inputRoomEvent)
 				if err != nil {
 					if !errors.Is(err, context.DeadlineExceeded) && !errors.Is(err, context.Canceled) {
 						sentry.CaptureException(err)
diff --git a/roomserver/internal/input/input_events.go b/roomserver/internal/input/input_events.go
index 16703616e..f3fa83d83 100644
--- a/roomserver/internal/input/input_events.go
+++ b/roomserver/internal/input/input_events.go
@@ -29,6 +29,7 @@ import (
 	"github.com/matrix-org/dendrite/roomserver/api"
 	"github.com/matrix-org/dendrite/roomserver/internal/helpers"
 	"github.com/matrix-org/dendrite/roomserver/state"
+	"github.com/matrix-org/dendrite/roomserver/storage/shared"
 	"github.com/matrix-org/dendrite/roomserver/types"
 	"github.com/matrix-org/gomatrixserverlib"
 	"github.com/matrix-org/util"
@@ -67,14 +68,15 @@ var processRoomEventDuration = prometheus.NewHistogramVec(
 // nolint:gocyclo
 func (r *Inputer) processRoomEvent(
 	ctx context.Context,
+	updater *shared.RoomUpdater,
 	input *api.InputRoomEvent,
-) (err error) {
+) (commitAction, error) {
 	select {
 	case <-ctx.Done():
 		// Before we do anything, make sure the context hasn't expired for this pending task.
 		// If it has then we'll give up straight away — it's probably a synchronous input
 		// request and the caller has already given up, but the inbox task was still queued.
-		return context.DeadlineExceeded
+		return rollbackTransaction, context.DeadlineExceeded
 	default:
 	}
 
@@ -107,7 +109,7 @@ func (r *Inputer) processRoomEvent(
 	// if we have already got this event then do not process it again, if the input kind is an outlier.
 	// Outliers contain no extra information which may warrant a re-processing.
 	if input.Kind == api.KindOutlier {
-		evs, err2 := r.DB.EventsFromIDs(ctx, []string{event.EventID()})
+		evs, err2 := updater.EventsFromIDs(ctx, []string{event.EventID()})
 		if err2 == nil && len(evs) == 1 {
 			// check hash matches if we're on early room versions where the event ID was a random string
 			idFormat, err2 := headered.RoomVersion.EventIDFormat()
@@ -116,11 +118,11 @@ func (r *Inputer) processRoomEvent(
 				case gomatrixserverlib.EventIDFormatV1:
 					if bytes.Equal(event.EventReference().EventSHA256, evs[0].EventReference().EventSHA256) {
 						logger.Debugf("Already processed event; ignoring")
-						return nil
+						return rollbackTransaction, nil
 					}
 				default:
 					logger.Debugf("Already processed event; ignoring")
-					return nil
+					return rollbackTransaction, nil
 				}
 			}
 		}
@@ -134,8 +136,8 @@ func (r *Inputer) processRoomEvent(
 			AuthEventIDs: event.AuthEventIDs(),
 			PrevEventIDs: event.PrevEventIDs(),
 		}
-		if err = r.Queryer.QueryMissingAuthPrevEvents(ctx, missingReq, missingRes); err != nil {
-			return fmt.Errorf("r.Queryer.QueryMissingAuthPrevEvents: %w", err)
+		if err := r.Queryer.QueryMissingAuthPrevEvents(ctx, missingReq, missingRes); err != nil {
+			return rollbackTransaction, fmt.Errorf("r.Queryer.QueryMissingAuthPrevEvents: %w", err)
 		}
 	}
 	missingAuth := len(missingRes.MissingAuthEventIDs) > 0
@@ -146,8 +148,8 @@ func (r *Inputer) processRoomEvent(
 			RoomID:      event.RoomID(),
 			ExcludeSelf: true,
 		}
-		if err = r.FSAPI.QueryJoinedHostServerNamesInRoom(ctx, serverReq, serverRes); err != nil {
-			return fmt.Errorf("r.FSAPI.QueryJoinedHostServerNamesInRoom: %w", err)
+		if err := r.FSAPI.QueryJoinedHostServerNamesInRoom(ctx, serverReq, serverRes); err != nil {
+			return rollbackTransaction, fmt.Errorf("r.FSAPI.QueryJoinedHostServerNamesInRoom: %w", err)
 		}
 		// Sort all of the servers into a map so that we can randomise
 		// their order. Then make sure that the input origin and the
@@ -176,8 +178,8 @@ func (r *Inputer) processRoomEvent(
 	isRejected := false
 	authEvents := gomatrixserverlib.NewAuthEvents(nil)
 	knownEvents := map[string]*types.Event{}
-	if err = r.fetchAuthEvents(ctx, logger, headered, &authEvents, knownEvents, serverRes.ServerNames); err != nil {
-		return fmt.Errorf("r.fetchAuthEvents: %w", err)
+	if err := r.fetchAuthEvents(ctx, updater, logger, headered, &authEvents, knownEvents, serverRes.ServerNames); err != nil {
+		return rollbackTransaction, fmt.Errorf("r.fetchAuthEvents: %w", err)
 	}
 
 	// Check if the event is allowed by its auth events. If it isn't then
@@ -193,7 +195,7 @@ func (r *Inputer) processRoomEvent(
 	authEventNIDs := make([]types.EventNID, 0, len(authEventIDs))
 	for _, authEventID := range authEventIDs {
 		if _, ok := knownEvents[authEventID]; !ok {
-			return fmt.Errorf("missing auth event %s", authEventID)
+			return rollbackTransaction, fmt.Errorf("missing auth event %s", authEventID)
 		}
 		authEventNIDs = append(authEventNIDs, knownEvents[authEventID].EventNID)
 	}
@@ -202,7 +204,8 @@ func (r *Inputer) processRoomEvent(
 	if input.Kind == api.KindNew {
 		// Check that the event passes authentication checks based on the
 		// current room state.
-		softfail, err = helpers.CheckForSoftFail(ctx, r.DB, headered, input.StateEventIDs)
+		var err error
+		softfail, err = helpers.CheckForSoftFail(ctx, updater, headered, input.StateEventIDs)
 		if err != nil {
 			logger.WithError(err).Warn("Error authing soft-failed event")
 		}
@@ -227,7 +230,7 @@ func (r *Inputer) processRoomEvent(
 				origin:     input.Origin,
 				inputer:    r,
 				queryer:    r.Queryer,
-				db:         r.DB,
+				db:         updater,
 				federation: r.FSAPI,
 				keys:       r.KeyRing,
 				roomsMu:    internal.NewMutexByRoom(),
@@ -235,7 +238,7 @@ func (r *Inputer) processRoomEvent(
 				hadEvents:  map[string]bool{},
 				haveEvents: map[string]*gomatrixserverlib.HeaderedEvent{},
 			}
-			if err = missingState.processEventWithMissingState(ctx, event, headered.RoomVersion); err != nil {
+			if err := missingState.processEventWithMissingState(ctx, event, headered.RoomVersion); err != nil {
 				isRejected = true
 				rejectionErr = fmt.Errorf("missingState.processEventWithMissingState: %w", err)
 			} else {
@@ -248,16 +251,16 @@ func (r *Inputer) processRoomEvent(
 	}
 
 	// Store the event.
-	_, _, stateAtEvent, redactionEvent, redactedEventID, err := r.DB.StoreEvent(ctx, event, authEventNIDs, isRejected)
+	_, _, stateAtEvent, redactionEvent, redactedEventID, err := updater.StoreEvent(ctx, event, authEventNIDs, isRejected)
 	if err != nil {
-		return fmt.Errorf("r.DB.StoreEvent: %w", err)
+		return rollbackTransaction, fmt.Errorf("updater.StoreEvent: %w", err)
 	}
 
 	// if storing this event results in it being redacted then do so.
 	if !isRejected && redactedEventID == event.EventID() {
 		r, rerr := eventutil.RedactEvent(redactionEvent, event)
 		if rerr != nil {
-			return fmt.Errorf("eventutil.RedactEvent: %w", rerr)
+			return rollbackTransaction, fmt.Errorf("eventutil.RedactEvent: %w", rerr)
 		}
 		event = r
 	}
@@ -268,23 +271,23 @@ func (r *Inputer) processRoomEvent(
 	if input.Kind == api.KindOutlier {
 		logger.Debug("Stored outlier")
 		hooks.Run(hooks.KindNewEventPersisted, headered)
-		return nil
+		return commitTransaction, nil
 	}
 
-	roomInfo, err := r.DB.RoomInfo(ctx, event.RoomID())
+	roomInfo, err := updater.RoomInfo(ctx, event.RoomID())
 	if err != nil {
-		return fmt.Errorf("r.DB.RoomInfo: %w", err)
+		return rollbackTransaction, fmt.Errorf("updater.RoomInfo: %w", err)
 	}
 	if roomInfo == nil {
-		return fmt.Errorf("r.DB.RoomInfo missing for room %s", event.RoomID())
+		return rollbackTransaction, fmt.Errorf("updater.RoomInfo missing for room %s", event.RoomID())
 	}
 
 	if !missingPrev && stateAtEvent.BeforeStateSnapshotNID == 0 {
 		// We haven't calculated a state for this event yet.
 		// Lets calculate one.
-		err = r.calculateAndSetState(ctx, input, roomInfo, &stateAtEvent, event, isRejected)
+		err = r.calculateAndSetState(ctx, updater, input, roomInfo, &stateAtEvent, event, isRejected)
 		if err != nil {
-			return fmt.Errorf("r.calculateAndSetState: %w", err)
+			return rollbackTransaction, fmt.Errorf("r.calculateAndSetState: %w", err)
 		}
 	}
 
@@ -294,13 +297,14 @@ func (r *Inputer) processRoomEvent(
 			"soft_fail":    softfail,
 			"missing_prev": missingPrev,
 		}).Warn("Stored rejected event")
-		return rejectionErr
+		return commitTransaction, rejectionErr
 	}
 
 	switch input.Kind {
 	case api.KindNew:
 		if err = r.updateLatestEvents(
 			ctx,                 // context
+			updater,             // room updater
 			roomInfo,            // room info for the room being updated
 			stateAtEvent,        // state at event (below)
 			event,               // event
@@ -308,7 +312,7 @@ func (r *Inputer) processRoomEvent(
 			input.TransactionID, // transaction ID
 			input.HasState,      // rewrites state?
 		); err != nil {
-			return fmt.Errorf("r.updateLatestEvents: %w", err)
+			return rollbackTransaction, fmt.Errorf("r.updateLatestEvents: %w", err)
 		}
 	case api.KindOld:
 		err = r.WriteOutputEvents(event.RoomID(), []api.OutputEvent{
@@ -320,7 +324,7 @@ func (r *Inputer) processRoomEvent(
 			},
 		})
 		if err != nil {
-			return fmt.Errorf("r.WriteOutputEvents (old): %w", err)
+			return rollbackTransaction, fmt.Errorf("r.WriteOutputEvents (old): %w", err)
 		}
 	}
 
@@ -339,14 +343,14 @@ func (r *Inputer) processRoomEvent(
 			},
 		})
 		if err != nil {
-			return fmt.Errorf("r.WriteOutputEvents (redactions): %w", err)
+			return rollbackTransaction, fmt.Errorf("r.WriteOutputEvents (redactions): %w", err)
 		}
 	}
 
 	// Everything was OK — the latest events updater didn't error and
 	// we've sent output events. Finally, generate a hook call.
 	hooks.Run(hooks.KindNewEventPersisted, headered)
-	return nil
+	return commitTransaction, nil
 }
 
 // fetchAuthEvents will check to see if any of the
@@ -358,6 +362,7 @@ func (r *Inputer) processRoomEvent(
 // they are now in the database.
 func (r *Inputer) fetchAuthEvents(
 	ctx context.Context,
+	updater *shared.RoomUpdater,
 	logger *logrus.Entry,
 	event *gomatrixserverlib.HeaderedEvent,
 	auth *gomatrixserverlib.AuthEvents,
@@ -375,7 +380,7 @@ func (r *Inputer) fetchAuthEvents(
 	}
 
 	for _, authEventID := range authEventIDs {
-		authEvents, err := r.DB.EventsFromIDs(ctx, []string{authEventID})
+		authEvents, err := updater.EventsFromIDs(ctx, []string{authEventID})
 		if err != nil || len(authEvents) == 0 || authEvents[0].Event == nil {
 			unknown[authEventID] = struct{}{}
 			continue
@@ -454,9 +459,9 @@ func (r *Inputer) fetchAuthEvents(
 		}
 
 		// Finally, store the event in the database.
-		eventNID, _, _, _, _, err := r.DB.StoreEvent(ctx, authEvent, authEventNIDs, isRejected)
+		eventNID, _, _, _, _, err := updater.StoreEvent(ctx, authEvent, authEventNIDs, isRejected)
 		if err != nil {
-			return fmt.Errorf("r.DB.StoreEvent: %w", err)
+			return fmt.Errorf("updater.StoreEvent: %w", err)
 		}
 
 		// Now we know about this event, it was stored and the signatures were OK.
@@ -471,6 +476,7 @@ func (r *Inputer) fetchAuthEvents(
 
 func (r *Inputer) calculateAndSetState(
 	ctx context.Context,
+	updater *shared.RoomUpdater,
 	input *api.InputRoomEvent,
 	roomInfo *types.RoomInfo,
 	stateAtEvent *types.StateAtEvent,
@@ -478,14 +484,14 @@ func (r *Inputer) calculateAndSetState(
 	isRejected bool,
 ) error {
 	var err error
-	roomState := state.NewStateResolution(r.DB, roomInfo)
+	roomState := state.NewStateResolution(updater, roomInfo)
 
 	if input.HasState {
 		// Check here if we think we're in the room already.
 		stateAtEvent.Overwrite = true
 		var joinEventNIDs []types.EventNID
 		// Request join memberships only for local users only.
-		if joinEventNIDs, err = r.DB.GetMembershipEventNIDsForRoom(ctx, roomInfo.RoomNID, true, true); err == nil {
+		if joinEventNIDs, err = updater.GetMembershipEventNIDsForRoom(ctx, roomInfo.RoomNID, true, true); err == nil {
 			// If we have no local users that are joined to the room then any state about
 			// the room that we have is quite possibly out of date. Therefore in that case
 			// we should overwrite it rather than merge it.
@@ -495,13 +501,13 @@ func (r *Inputer) calculateAndSetState(
 		// We've been told what the state at the event is so we don't need to calculate it.
 		// Check that those state events are in the database and store the state.
 		var entries []types.StateEntry
-		if entries, err = r.DB.StateEntriesForEventIDs(ctx, input.StateEventIDs); err != nil {
-			return fmt.Errorf("r.DB.StateEntriesForEventIDs: %w", err)
+		if entries, err = updater.StateEntriesForEventIDs(ctx, input.StateEventIDs); err != nil {
+			return fmt.Errorf("updater.StateEntriesForEventIDs: %w", err)
 		}
 		entries = types.DeduplicateStateEntries(entries)
 
-		if stateAtEvent.BeforeStateSnapshotNID, err = r.DB.AddState(ctx, roomInfo.RoomNID, nil, entries); err != nil {
-			return fmt.Errorf("r.DB.AddState: %w", err)
+		if stateAtEvent.BeforeStateSnapshotNID, err = updater.AddState(ctx, roomInfo.RoomNID, nil, entries); err != nil {
+			return fmt.Errorf("updater.AddState: %w", err)
 		}
 	} else {
 		stateAtEvent.Overwrite = false
@@ -512,7 +518,7 @@ func (r *Inputer) calculateAndSetState(
 		}
 	}
 
-	err = r.DB.SetState(ctx, stateAtEvent.EventNID, stateAtEvent.BeforeStateSnapshotNID)
+	err = updater.SetState(ctx, stateAtEvent.EventNID, stateAtEvent.BeforeStateSnapshotNID)
 	if err != nil {
 		return fmt.Errorf("r.DB.SetState: %w", err)
 	}
diff --git a/roomserver/internal/input/input_latest_events.go b/roomserver/internal/input/input_latest_events.go
index 6137941e1..5173d3ab2 100644
--- a/roomserver/internal/input/input_latest_events.go
+++ b/roomserver/internal/input/input_latest_events.go
@@ -20,7 +20,6 @@ import (
 	"context"
 	"fmt"
 
-	"github.com/matrix-org/dendrite/internal/sqlutil"
 	"github.com/matrix-org/dendrite/roomserver/api"
 	"github.com/matrix-org/dendrite/roomserver/state"
 	"github.com/matrix-org/dendrite/roomserver/storage/shared"
@@ -48,6 +47,7 @@ import (
 // Can only be called once at a time
 func (r *Inputer) updateLatestEvents(
 	ctx context.Context,
+	updater *shared.RoomUpdater,
 	roomInfo *types.RoomInfo,
 	stateAtEvent types.StateAtEvent,
 	event *gomatrixserverlib.Event,
@@ -55,13 +55,6 @@ func (r *Inputer) updateLatestEvents(
 	transactionID *api.TransactionID,
 	rewritesState bool,
 ) (err error) {
-	updater, err := r.DB.GetLatestEventsForUpdate(ctx, *roomInfo)
-	if err != nil {
-		return fmt.Errorf("r.DB.GetLatestEventsForUpdate: %w", err)
-	}
-	succeeded := false
-	defer sqlutil.EndTransactionWithCheck(updater, &succeeded, &err)
-
 	u := latestEventsUpdater{
 		ctx:           ctx,
 		api:           r,
@@ -78,7 +71,6 @@ func (r *Inputer) updateLatestEvents(
 		return fmt.Errorf("u.doUpdateLatestEvents: %w", err)
 	}
 
-	succeeded = true
 	return
 }
 
@@ -89,7 +81,7 @@ func (r *Inputer) updateLatestEvents(
 type latestEventsUpdater struct {
 	ctx           context.Context
 	api           *Inputer
-	updater       *shared.LatestEventsUpdater
+	updater       *shared.RoomUpdater
 	roomInfo      *types.RoomInfo
 	stateAtEvent  types.StateAtEvent
 	event         *gomatrixserverlib.Event
@@ -199,7 +191,7 @@ func (u *latestEventsUpdater) doUpdateLatestEvents() error {
 
 func (u *latestEventsUpdater) latestState() error {
 	var err error
-	roomState := state.NewStateResolution(u.api.DB, u.roomInfo)
+	roomState := state.NewStateResolution(u.updater, u.roomInfo)
 
 	// Work out if the state at the extremities has actually changed
 	// or not. If they haven't then we won't bother doing all of the
@@ -413,7 +405,7 @@ func (u *latestEventsUpdater) extraEventsForIDs(roomVersion gomatrixserverlib.Ro
 	if len(extraEventIDs) == 0 {
 		return nil, nil
 	}
-	extraEvents, err := u.api.DB.EventsFromIDs(u.ctx, extraEventIDs)
+	extraEvents, err := u.updater.EventsFromIDs(u.ctx, extraEventIDs)
 	if err != nil {
 		return nil, err
 	}
@@ -436,7 +428,7 @@ func (u *latestEventsUpdater) stateEventMap() (map[types.EventNID]string, error)
 		stateEventNIDs = append(stateEventNIDs, entry.EventNID)
 	}
 	stateEventNIDs = stateEventNIDs[:util.SortAndUnique(eventNIDSorter(stateEventNIDs))]
-	return u.api.DB.EventIDs(u.ctx, stateEventNIDs)
+	return u.updater.EventIDs(u.ctx, stateEventNIDs)
 }
 
 type eventNIDSorter []types.EventNID
diff --git a/roomserver/internal/input/input_membership.go b/roomserver/internal/input/input_membership.go
index 2511097d0..ff3ed7e5d 100644
--- a/roomserver/internal/input/input_membership.go
+++ b/roomserver/internal/input/input_membership.go
@@ -31,7 +31,7 @@ import (
 // consumers about the invites added or retired by the change in current state.
 func (r *Inputer) updateMemberships(
 	ctx context.Context,
-	updater *shared.LatestEventsUpdater,
+	updater *shared.RoomUpdater,
 	removed, added []types.StateEntry,
 ) ([]api.OutputEvent, error) {
 	changes := membershipChanges(removed, added)
@@ -79,7 +79,7 @@ func (r *Inputer) updateMemberships(
 }
 
 func (r *Inputer) updateMembership(
-	updater *shared.LatestEventsUpdater,
+	updater *shared.RoomUpdater,
 	targetUserNID types.EventStateKeyNID,
 	remove, add *gomatrixserverlib.Event,
 	updates []api.OutputEvent,
diff --git a/roomserver/internal/input/input_missing.go b/roomserver/internal/input/input_missing.go
index d401fa0e9..4cd2b3de1 100644
--- a/roomserver/internal/input/input_missing.go
+++ b/roomserver/internal/input/input_missing.go
@@ -11,7 +11,7 @@ import (
 	"github.com/matrix-org/dendrite/internal"
 	"github.com/matrix-org/dendrite/roomserver/api"
 	"github.com/matrix-org/dendrite/roomserver/internal/query"
-	"github.com/matrix-org/dendrite/roomserver/storage"
+	"github.com/matrix-org/dendrite/roomserver/storage/shared"
 	"github.com/matrix-org/gomatrixserverlib"
 	"github.com/matrix-org/util"
 	"github.com/sirupsen/logrus"
@@ -19,7 +19,7 @@ import (
 
 type missingStateReq struct {
 	origin          gomatrixserverlib.ServerName
-	db              storage.Database
+	db              *shared.RoomUpdater
 	inputer         *Inputer
 	queryer         *query.Queryer
 	keys            gomatrixserverlib.JSONVerifier
@@ -78,7 +78,7 @@ func (t *missingStateReq) processEventWithMissingState(
 		// we can just inject all the newEvents as new as we may have only missed 1 or 2 events and have filled
 		// in the gap in the DAG
 		for _, newEvent := range newEvents {
-			err = t.inputer.processRoomEvent(ctx, &api.InputRoomEvent{
+			_, err = t.inputer.processRoomEvent(ctx, t.db, &api.InputRoomEvent{
 				Kind:         api.KindNew,
 				Event:        newEvent.Headered(roomVersion),
 				Origin:       t.origin,
@@ -187,7 +187,7 @@ func (t *missingStateReq) processEventWithMissingState(
 	}
 	// TODO: we could do this concurrently?
 	for _, ire := range outlierRoomEvents {
-		if err = t.inputer.processRoomEvent(ctx, &ire); err != nil {
+		if _, err = t.inputer.processRoomEvent(ctx, t.db, &ire); err != nil {
 			return fmt.Errorf("t.inputer.processRoomEvent[outlier]: %w", err)
 		}
 	}
@@ -200,7 +200,7 @@ func (t *missingStateReq) processEventWithMissingState(
 		stateIDs = append(stateIDs, event.EventID())
 	}
 
-	err = t.inputer.processRoomEvent(ctx, &api.InputRoomEvent{
+	_, err = t.inputer.processRoomEvent(ctx, t.db, &api.InputRoomEvent{
 		Kind:          api.KindOld,
 		Event:         backwardsExtremity.Headered(roomVersion),
 		Origin:        t.origin,
@@ -217,7 +217,7 @@ func (t *missingStateReq) processEventWithMissingState(
 	// they will automatically fast-forward based on the room state at the
 	// extremity in the last step.
 	for _, newEvent := range newEvents {
-		err = t.inputer.processRoomEvent(ctx, &api.InputRoomEvent{
+		_, err = t.inputer.processRoomEvent(ctx, t.db, &api.InputRoomEvent{
 			Kind:         api.KindOld,
 			Event:        newEvent.Headered(roomVersion),
 			Origin:       t.origin,
diff --git a/roomserver/state/state.go b/roomserver/state/state.go
index 15d592b46..e5f69521e 100644
--- a/roomserver/state/state.go
+++ b/roomserver/state/state.go
@@ -22,7 +22,6 @@ import (
 	"sort"
 	"time"
 
-	"github.com/matrix-org/dendrite/roomserver/storage"
 	"github.com/matrix-org/util"
 	"github.com/prometheus/client_golang/prometheus"
 
@@ -30,13 +29,25 @@ import (
 	"github.com/matrix-org/gomatrixserverlib"
 )
 
+type StateResolutionStorage interface {
+	EventTypeNIDs(ctx context.Context, eventTypes []string) (map[string]types.EventTypeNID, error)
+	EventStateKeyNIDs(ctx context.Context, eventStateKeys []string) (map[string]types.EventStateKeyNID, error)
+	StateBlockNIDs(ctx context.Context, stateNIDs []types.StateSnapshotNID) ([]types.StateBlockNIDList, error)
+	StateEntries(ctx context.Context, stateBlockNIDs []types.StateBlockNID) ([]types.StateEntryList, error)
+	SnapshotNIDFromEventID(ctx context.Context, eventID string) (types.StateSnapshotNID, error)
+	StateEntriesForTuples(ctx context.Context, stateBlockNIDs []types.StateBlockNID, stateKeyTuples []types.StateKeyTuple) ([]types.StateEntryList, error)
+	StateAtEventIDs(ctx context.Context, eventIDs []string) ([]types.StateAtEvent, error)
+	AddState(ctx context.Context, roomNID types.RoomNID, stateBlockNIDs []types.StateBlockNID, state []types.StateEntry) (types.StateSnapshotNID, error)
+	Events(ctx context.Context, eventNIDs []types.EventNID) ([]types.Event, error)
+}
+
 type StateResolution struct {
-	db       storage.Database
+	db       StateResolutionStorage
 	roomInfo *types.RoomInfo
 	events   map[types.EventNID]*gomatrixserverlib.Event
 }
 
-func NewStateResolution(db storage.Database, roomInfo *types.RoomInfo) StateResolution {
+func NewStateResolution(db StateResolutionStorage, roomInfo *types.RoomInfo) StateResolution {
 	return StateResolution{
 		db:       db,
 		roomInfo: roomInfo,
diff --git a/roomserver/storage/interface.go b/roomserver/storage/interface.go
index 15764366b..a9851e05b 100644
--- a/roomserver/storage/interface.go
+++ b/roomserver/storage/interface.go
@@ -86,11 +86,10 @@ type Database interface {
 	// Lookup the event IDs for a batch of event numeric IDs.
 	// Returns an error if the retrieval went wrong.
 	EventIDs(ctx context.Context, eventNIDs []types.EventNID) (map[types.EventNID]string, error)
-	// Look up the latest events in a room in preparation for an update.
-	// The RoomRecentEventsUpdater must have Commit or Rollback called on it if this doesn't return an error.
-	// Returns the latest events in the room and the last eventID sent to the log along with an updater.
+	// Opens and returns a room updater, which locks the room and opens a transaction.
+	// The GetRoomUpdater must have Commit or Rollback called on it if this doesn't return an error.
 	// If this returns an error then no further action is required.
-	GetLatestEventsForUpdate(ctx context.Context, roomInfo types.RoomInfo) (*shared.LatestEventsUpdater, error)
+	GetRoomUpdater(ctx context.Context, roomInfo *types.RoomInfo) (*shared.RoomUpdater, error)
 	// Look up event references for the latest events in the room and the current state snapshot.
 	// Returns the latest events, the current state and the maximum depth of the latest events plus 1.
 	// Returns an error if there was a problem talking to the database.
diff --git a/roomserver/storage/postgres/event_json_table.go b/roomserver/storage/postgres/event_json_table.go
index 32e457821..433e445d8 100644
--- a/roomserver/storage/postgres/event_json_table.go
+++ b/roomserver/storage/postgres/event_json_table.go
@@ -81,9 +81,10 @@ func (s *eventJSONStatements) InsertEventJSON(
 }
 
 func (s *eventJSONStatements) BulkSelectEventJSON(
-	ctx context.Context, eventNIDs []types.EventNID,
+	ctx context.Context, txn *sql.Tx, eventNIDs []types.EventNID,
 ) ([]tables.EventJSONPair, error) {
-	rows, err := s.bulkSelectEventJSONStmt.QueryContext(ctx, eventNIDsAsArray(eventNIDs))
+	stmt := sqlutil.TxStmt(txn, s.bulkSelectEventJSONStmt)
+	rows, err := stmt.QueryContext(ctx, eventNIDsAsArray(eventNIDs))
 	if err != nil {
 		return nil, err
 	}
diff --git a/roomserver/storage/postgres/event_state_keys_table.go b/roomserver/storage/postgres/event_state_keys_table.go
index 3a7cf03e3..762b3a1fc 100644
--- a/roomserver/storage/postgres/event_state_keys_table.go
+++ b/roomserver/storage/postgres/event_state_keys_table.go
@@ -111,9 +111,10 @@ func (s *eventStateKeyStatements) SelectEventStateKeyNID(
 }
 
 func (s *eventStateKeyStatements) BulkSelectEventStateKeyNID(
-	ctx context.Context, eventStateKeys []string,
+	ctx context.Context, txn *sql.Tx, eventStateKeys []string,
 ) (map[string]types.EventStateKeyNID, error) {
-	rows, err := s.bulkSelectEventStateKeyNIDStmt.QueryContext(
+	stmt := sqlutil.TxStmt(txn, s.bulkSelectEventStateKeyNIDStmt)
+	rows, err := stmt.QueryContext(
 		ctx, pq.StringArray(eventStateKeys),
 	)
 	if err != nil {
@@ -134,13 +135,14 @@ func (s *eventStateKeyStatements) BulkSelectEventStateKeyNID(
 }
 
 func (s *eventStateKeyStatements) BulkSelectEventStateKey(
-	ctx context.Context, eventStateKeyNIDs []types.EventStateKeyNID,
+	ctx context.Context, txn *sql.Tx, eventStateKeyNIDs []types.EventStateKeyNID,
 ) (map[types.EventStateKeyNID]string, error) {
 	nIDs := make(pq.Int64Array, len(eventStateKeyNIDs))
 	for i := range eventStateKeyNIDs {
 		nIDs[i] = int64(eventStateKeyNIDs[i])
 	}
-	rows, err := s.bulkSelectEventStateKeyStmt.QueryContext(ctx, nIDs)
+	stmt := sqlutil.TxStmt(txn, s.bulkSelectEventStateKeyStmt)
+	rows, err := stmt.QueryContext(ctx, nIDs)
 	if err != nil {
 		return nil, err
 	}
diff --git a/roomserver/storage/postgres/event_types_table.go b/roomserver/storage/postgres/event_types_table.go
index e558072a5..1d5de5822 100644
--- a/roomserver/storage/postgres/event_types_table.go
+++ b/roomserver/storage/postgres/event_types_table.go
@@ -133,9 +133,10 @@ func (s *eventTypeStatements) SelectEventTypeNID(
 }
 
 func (s *eventTypeStatements) BulkSelectEventTypeNID(
-	ctx context.Context, eventTypes []string,
+	ctx context.Context, txn *sql.Tx, eventTypes []string,
 ) (map[string]types.EventTypeNID, error) {
-	rows, err := s.bulkSelectEventTypeNIDStmt.QueryContext(ctx, pq.StringArray(eventTypes))
+	stmt := sqlutil.TxStmt(txn, s.bulkSelectEventTypeNIDStmt)
+	rows, err := stmt.QueryContext(ctx, pq.StringArray(eventTypes))
 	if err != nil {
 		return nil, err
 	}
diff --git a/roomserver/storage/postgres/events_table.go b/roomserver/storage/postgres/events_table.go
index 778cd8d73..6c3847752 100644
--- a/roomserver/storage/postgres/events_table.go
+++ b/roomserver/storage/postgres/events_table.go
@@ -212,9 +212,10 @@ func (s *eventStatements) SelectEvent(
 // bulkSelectStateEventByID lookups a list of state events by event ID.
 // If any of the requested events are missing from the database it returns a types.MissingEventError
 func (s *eventStatements) BulkSelectStateEventByID(
-	ctx context.Context, eventIDs []string,
+	ctx context.Context, txn *sql.Tx, eventIDs []string,
 ) ([]types.StateEntry, error) {
-	rows, err := s.bulkSelectStateEventByIDStmt.QueryContext(ctx, pq.StringArray(eventIDs))
+	stmt := sqlutil.TxStmt(txn, s.bulkSelectStateEventByIDStmt)
+	rows, err := stmt.QueryContext(ctx, pq.StringArray(eventIDs))
 	if err != nil {
 		return nil, err
 	}
@@ -254,13 +255,14 @@ func (s *eventStatements) BulkSelectStateEventByID(
 // bulkSelectStateEventByNID lookups a list of state events by event NID.
 // If any of the requested events are missing from the database it returns a types.MissingEventError
 func (s *eventStatements) BulkSelectStateEventByNID(
-	ctx context.Context, eventNIDs []types.EventNID,
+	ctx context.Context, txn *sql.Tx, eventNIDs []types.EventNID,
 	stateKeyTuples []types.StateKeyTuple,
 ) ([]types.StateEntry, error) {
 	tuples := stateKeyTupleSorter(stateKeyTuples)
 	sort.Sort(tuples)
 	eventTypeNIDArray, eventStateKeyNIDArray := tuples.typesAndStateKeysAsArrays()
-	rows, err := s.bulkSelectStateEventByNIDStmt.QueryContext(ctx, eventNIDsAsArray(eventNIDs), eventTypeNIDArray, eventStateKeyNIDArray)
+	stmt := sqlutil.TxStmt(txn, s.bulkSelectStateEventByNIDStmt)
+	rows, err := stmt.QueryContext(ctx, eventNIDsAsArray(eventNIDs), eventTypeNIDArray, eventStateKeyNIDArray)
 	if err != nil {
 		return nil, err
 	}
@@ -291,9 +293,10 @@ func (s *eventStatements) BulkSelectStateEventByNID(
 // If any of the requested events are missing from the database it returns a types.MissingEventError.
 // If we do not have the state for any of the requested events it returns a types.MissingEventError.
 func (s *eventStatements) BulkSelectStateAtEventByID(
-	ctx context.Context, eventIDs []string,
+	ctx context.Context, txn *sql.Tx, eventIDs []string,
 ) ([]types.StateAtEvent, error) {
-	rows, err := s.bulkSelectStateAtEventByIDStmt.QueryContext(ctx, pq.StringArray(eventIDs))
+	stmt := sqlutil.TxStmt(txn, s.bulkSelectStateAtEventByIDStmt)
+	rows, err := stmt.QueryContext(ctx, pq.StringArray(eventIDs))
 	if err != nil {
 		return nil, err
 	}
@@ -428,8 +431,9 @@ func (s *eventStatements) BulkSelectEventReference(
 }
 
 // bulkSelectEventID returns a map from numeric event ID to string event ID.
-func (s *eventStatements) BulkSelectEventID(ctx context.Context, eventNIDs []types.EventNID) (map[types.EventNID]string, error) {
-	rows, err := s.bulkSelectEventIDStmt.QueryContext(ctx, eventNIDsAsArray(eventNIDs))
+func (s *eventStatements) BulkSelectEventID(ctx context.Context, txn *sql.Tx, eventNIDs []types.EventNID) (map[types.EventNID]string, error) {
+	stmt := sqlutil.TxStmt(txn, s.bulkSelectEventIDStmt)
+	rows, err := stmt.QueryContext(ctx, eventNIDsAsArray(eventNIDs))
 	if err != nil {
 		return nil, err
 	}
@@ -455,8 +459,9 @@ func (s *eventStatements) BulkSelectEventID(ctx context.Context, eventNIDs []typ
 
 // bulkSelectEventNIDs returns a map from string event ID to numeric event ID.
 // If an event ID is not in the database then it is omitted from the map.
-func (s *eventStatements) BulkSelectEventNID(ctx context.Context, eventIDs []string) (map[string]types.EventNID, error) {
-	rows, err := s.bulkSelectEventNIDStmt.QueryContext(ctx, pq.StringArray(eventIDs))
+func (s *eventStatements) BulkSelectEventNID(ctx context.Context, txn *sql.Tx, eventIDs []string) (map[string]types.EventNID, error) {
+	stmt := sqlutil.TxStmt(txn, s.bulkSelectEventNIDStmt)
+	rows, err := stmt.QueryContext(ctx, pq.StringArray(eventIDs))
 	if err != nil {
 		return nil, err
 	}
@@ -484,9 +489,10 @@ func (s *eventStatements) SelectMaxEventDepth(ctx context.Context, txn *sql.Tx,
 }
 
 func (s *eventStatements) SelectRoomNIDsForEventNIDs(
-	ctx context.Context, eventNIDs []types.EventNID,
+	ctx context.Context, txn *sql.Tx, eventNIDs []types.EventNID,
 ) (map[types.EventNID]types.RoomNID, error) {
-	rows, err := s.selectRoomNIDsForEventNIDsStmt.QueryContext(ctx, eventNIDsAsArray(eventNIDs))
+	stmt := sqlutil.TxStmt(txn, s.selectRoomNIDsForEventNIDsStmt)
+	rows, err := stmt.QueryContext(ctx, eventNIDsAsArray(eventNIDs))
 	if err != nil {
 		return nil, err
 	}
diff --git a/roomserver/storage/postgres/invite_table.go b/roomserver/storage/postgres/invite_table.go
index 344302c8f..176c16e48 100644
--- a/roomserver/storage/postgres/invite_table.go
+++ b/roomserver/storage/postgres/invite_table.go
@@ -97,8 +97,8 @@ func prepareInvitesTable(db *sql.DB) (tables.Invites, error) {
 }
 
 func (s *inviteStatements) InsertInviteEvent(
-	ctx context.Context,
-	txn *sql.Tx, inviteEventID string, roomNID types.RoomNID,
+	ctx context.Context, txn *sql.Tx,
+	inviteEventID string, roomNID types.RoomNID,
 	targetUserNID, senderUserNID types.EventStateKeyNID,
 	inviteEventJSON []byte,
 ) (bool, error) {
@@ -116,8 +116,8 @@ func (s *inviteStatements) InsertInviteEvent(
 }
 
 func (s *inviteStatements) UpdateInviteRetired(
-	ctx context.Context,
-	txn *sql.Tx, roomNID types.RoomNID, targetUserNID types.EventStateKeyNID,
+	ctx context.Context, txn *sql.Tx,
+	roomNID types.RoomNID, targetUserNID types.EventStateKeyNID,
 ) ([]string, error) {
 	stmt := sqlutil.TxStmt(txn, s.updateInviteRetiredStmt)
 	rows, err := stmt.QueryContext(ctx, roomNID, targetUserNID)
@@ -139,10 +139,11 @@ func (s *inviteStatements) UpdateInviteRetired(
 
 // SelectInviteActiveForUserInRoom returns a list of sender state key NIDs
 func (s *inviteStatements) SelectInviteActiveForUserInRoom(
-	ctx context.Context,
+	ctx context.Context, txn *sql.Tx,
 	targetUserNID types.EventStateKeyNID, roomNID types.RoomNID,
 ) ([]types.EventStateKeyNID, []string, error) {
-	rows, err := s.selectInviteActiveForUserInRoomStmt.QueryContext(
+	stmt := sqlutil.TxStmt(txn, s.selectInviteActiveForUserInRoomStmt)
+	rows, err := stmt.QueryContext(
 		ctx, targetUserNID, roomNID,
 	)
 	if err != nil {
diff --git a/roomserver/storage/postgres/membership_table.go b/roomserver/storage/postgres/membership_table.go
index b0d906c80..48c2c35cd 100644
--- a/roomserver/storage/postgres/membership_table.go
+++ b/roomserver/storage/postgres/membership_table.go
@@ -186,8 +186,8 @@ func prepareMembershipTable(db *sql.DB) (tables.Membership, error) {
 }
 
 func (s *membershipStatements) InsertMembership(
-	ctx context.Context,
-	txn *sql.Tx, roomNID types.RoomNID, targetUserNID types.EventStateKeyNID,
+	ctx context.Context, txn *sql.Tx,
+	roomNID types.RoomNID, targetUserNID types.EventStateKeyNID,
 	localTarget bool,
 ) error {
 	stmt := sqlutil.TxStmt(txn, s.insertMembershipStmt)
@@ -196,8 +196,8 @@ func (s *membershipStatements) InsertMembership(
 }
 
 func (s *membershipStatements) SelectMembershipForUpdate(
-	ctx context.Context,
-	txn *sql.Tx, roomNID types.RoomNID, targetUserNID types.EventStateKeyNID,
+	ctx context.Context, txn *sql.Tx,
+	roomNID types.RoomNID, targetUserNID types.EventStateKeyNID,
 ) (membership tables.MembershipState, err error) {
 	err = sqlutil.TxStmt(txn, s.selectMembershipForUpdateStmt).QueryRowContext(
 		ctx, roomNID, targetUserNID,
@@ -206,17 +206,19 @@ func (s *membershipStatements) SelectMembershipForUpdate(
 }
 
 func (s *membershipStatements) SelectMembershipFromRoomAndTarget(
-	ctx context.Context,
+	ctx context.Context, txn *sql.Tx,
 	roomNID types.RoomNID, targetUserNID types.EventStateKeyNID,
 ) (eventNID types.EventNID, membership tables.MembershipState, forgotten bool, err error) {
-	err = s.selectMembershipFromRoomAndTargetStmt.QueryRowContext(
+	stmt := sqlutil.TxStmt(txn, s.selectMembershipFromRoomAndTargetStmt)
+	err = stmt.QueryRowContext(
 		ctx, roomNID, targetUserNID,
 	).Scan(&membership, &eventNID, &forgotten)
 	return
 }
 
 func (s *membershipStatements) SelectMembershipsFromRoom(
-	ctx context.Context, roomNID types.RoomNID, localOnly bool,
+	ctx context.Context, txn *sql.Tx,
+	roomNID types.RoomNID, localOnly bool,
 ) (eventNIDs []types.EventNID, err error) {
 	var stmt *sql.Stmt
 	if localOnly {
@@ -224,6 +226,7 @@ func (s *membershipStatements) SelectMembershipsFromRoom(
 	} else {
 		stmt = s.selectMembershipsFromRoomStmt
 	}
+	stmt = sqlutil.TxStmt(txn, stmt)
 	rows, err := stmt.QueryContext(ctx, roomNID)
 	if err != nil {
 		return
@@ -241,7 +244,7 @@ func (s *membershipStatements) SelectMembershipsFromRoom(
 }
 
 func (s *membershipStatements) SelectMembershipsFromRoomAndMembership(
-	ctx context.Context,
+	ctx context.Context, txn *sql.Tx,
 	roomNID types.RoomNID, membership tables.MembershipState, localOnly bool,
 ) (eventNIDs []types.EventNID, err error) {
 	var rows *sql.Rows
@@ -251,6 +254,7 @@ func (s *membershipStatements) SelectMembershipsFromRoomAndMembership(
 	} else {
 		stmt = s.selectMembershipsFromRoomAndMembershipStmt
 	}
+	stmt = sqlutil.TxStmt(txn, stmt)
 	rows, err = stmt.QueryContext(ctx, roomNID, membership)
 	if err != nil {
 		return
@@ -268,8 +272,8 @@ func (s *membershipStatements) SelectMembershipsFromRoomAndMembership(
 }
 
 func (s *membershipStatements) UpdateMembership(
-	ctx context.Context,
-	txn *sql.Tx, roomNID types.RoomNID, targetUserNID types.EventStateKeyNID, senderUserNID types.EventStateKeyNID, membership tables.MembershipState,
+	ctx context.Context, txn *sql.Tx,
+	roomNID types.RoomNID, targetUserNID types.EventStateKeyNID, senderUserNID types.EventStateKeyNID, membership tables.MembershipState,
 	eventNID types.EventNID, forgotten bool,
 ) error {
 	_, err := sqlutil.TxStmt(txn, s.updateMembershipStmt).ExecContext(
@@ -279,9 +283,11 @@ func (s *membershipStatements) UpdateMembership(
 }
 
 func (s *membershipStatements) SelectRoomsWithMembership(
-	ctx context.Context, userID types.EventStateKeyNID, membershipState tables.MembershipState,
+	ctx context.Context, txn *sql.Tx,
+	userID types.EventStateKeyNID, membershipState tables.MembershipState,
 ) ([]types.RoomNID, error) {
-	rows, err := s.selectRoomsWithMembershipStmt.QueryContext(ctx, membershipState, userID)
+	stmt := sqlutil.TxStmt(txn, s.selectRoomsWithMembershipStmt)
+	rows, err := stmt.QueryContext(ctx, membershipState, userID)
 	if err != nil {
 		return nil, err
 	}
@@ -297,12 +303,16 @@ func (s *membershipStatements) SelectRoomsWithMembership(
 	return roomNIDs, nil
 }
 
-func (s *membershipStatements) SelectJoinedUsersSetForRooms(ctx context.Context, roomNIDs []types.RoomNID) (map[types.EventStateKeyNID]int, error) {
+func (s *membershipStatements) SelectJoinedUsersSetForRooms(
+	ctx context.Context, txn *sql.Tx,
+	roomNIDs []types.RoomNID,
+) (map[types.EventStateKeyNID]int, error) {
 	roomIDarray := make([]int64, len(roomNIDs))
 	for i := range roomNIDs {
 		roomIDarray[i] = int64(roomNIDs[i])
 	}
-	rows, err := s.selectJoinedUsersSetForRoomsStmt.QueryContext(ctx, pq.Int64Array(roomIDarray))
+	stmt := sqlutil.TxStmt(txn, s.selectJoinedUsersSetForRoomsStmt)
+	rows, err := stmt.QueryContext(ctx, pq.Int64Array(roomIDarray))
 	if err != nil {
 		return nil, err
 	}
@@ -319,8 +329,12 @@ func (s *membershipStatements) SelectJoinedUsersSetForRooms(ctx context.Context,
 	return result, rows.Err()
 }
 
-func (s *membershipStatements) SelectKnownUsers(ctx context.Context, userID types.EventStateKeyNID, searchString string, limit int) ([]string, error) {
-	rows, err := s.selectKnownUsersStmt.QueryContext(ctx, userID, fmt.Sprintf("%%%s%%", searchString), limit)
+func (s *membershipStatements) SelectKnownUsers(
+	ctx context.Context, txn *sql.Tx,
+	userID types.EventStateKeyNID, searchString string, limit int,
+) ([]string, error) {
+	stmt := sqlutil.TxStmt(txn, s.selectKnownUsersStmt)
+	rows, err := stmt.QueryContext(ctx, userID, fmt.Sprintf("%%%s%%", searchString), limit)
 	if err != nil {
 		return nil, err
 	}
@@ -337,9 +351,8 @@ func (s *membershipStatements) SelectKnownUsers(ctx context.Context, userID type
 }
 
 func (s *membershipStatements) UpdateForgetMembership(
-	ctx context.Context,
-	txn *sql.Tx, roomNID types.RoomNID, targetUserNID types.EventStateKeyNID,
-	forget bool,
+	ctx context.Context, txn *sql.Tx,
+	roomNID types.RoomNID, targetUserNID types.EventStateKeyNID, forget bool,
 ) error {
 	_, err := sqlutil.TxStmt(txn, s.updateMembershipForgetRoomStmt).ExecContext(
 		ctx, roomNID, targetUserNID, forget,
@@ -347,9 +360,13 @@ func (s *membershipStatements) UpdateForgetMembership(
 	return err
 }
 
-func (s *membershipStatements) SelectLocalServerInRoom(ctx context.Context, roomNID types.RoomNID) (bool, error) {
+func (s *membershipStatements) SelectLocalServerInRoom(
+	ctx context.Context, txn *sql.Tx,
+	roomNID types.RoomNID,
+) (bool, error) {
 	var nid types.RoomNID
-	err := s.selectLocalServerInRoomStmt.QueryRowContext(ctx, tables.MembershipStateJoin, roomNID).Scan(&nid)
+	stmt := sqlutil.TxStmt(txn, s.selectLocalServerInRoomStmt)
+	err := stmt.QueryRowContext(ctx, tables.MembershipStateJoin, roomNID).Scan(&nid)
 	if err != nil {
 		if err == sql.ErrNoRows {
 			return false, nil
@@ -360,9 +377,13 @@ func (s *membershipStatements) SelectLocalServerInRoom(ctx context.Context, room
 	return found, nil
 }
 
-func (s *membershipStatements) SelectServerInRoom(ctx context.Context, roomNID types.RoomNID, serverName gomatrixserverlib.ServerName) (bool, error) {
+func (s *membershipStatements) SelectServerInRoom(
+	ctx context.Context, txn *sql.Tx,
+	roomNID types.RoomNID, serverName gomatrixserverlib.ServerName,
+) (bool, error) {
 	var nid types.RoomNID
-	err := s.selectServerInRoomStmt.QueryRowContext(ctx, tables.MembershipStateJoin, roomNID, serverName).Scan(&nid)
+	stmt := sqlutil.TxStmt(txn, s.selectServerInRoomStmt)
+	err := stmt.QueryRowContext(ctx, tables.MembershipStateJoin, roomNID, serverName).Scan(&nid)
 	if err != nil {
 		if err == sql.ErrNoRows {
 			return false, nil
diff --git a/roomserver/storage/postgres/published_table.go b/roomserver/storage/postgres/published_table.go
index 8deb68441..15985fcd6 100644
--- a/roomserver/storage/postgres/published_table.go
+++ b/roomserver/storage/postgres/published_table.go
@@ -73,9 +73,10 @@ func (s *publishedStatements) UpsertRoomPublished(
 }
 
 func (s *publishedStatements) SelectPublishedFromRoomID(
-	ctx context.Context, roomID string,
+	ctx context.Context, txn *sql.Tx, roomID string,
 ) (published bool, err error) {
-	err = s.selectPublishedStmt.QueryRowContext(ctx, roomID).Scan(&published)
+	stmt := sqlutil.TxStmt(txn, s.selectPublishedStmt)
+	err = stmt.QueryRowContext(ctx, roomID).Scan(&published)
 	if err == sql.ErrNoRows {
 		return false, nil
 	}
@@ -83,9 +84,10 @@ func (s *publishedStatements) SelectPublishedFromRoomID(
 }
 
 func (s *publishedStatements) SelectAllPublishedRooms(
-	ctx context.Context, published bool,
+	ctx context.Context, txn *sql.Tx, published bool,
 ) ([]string, error) {
-	rows, err := s.selectAllPublishedStmt.QueryContext(ctx, published)
+	stmt := sqlutil.TxStmt(txn, s.selectAllPublishedStmt)
+	rows, err := stmt.QueryContext(ctx, published)
 	if err != nil {
 		return nil, err
 	}
diff --git a/roomserver/storage/postgres/room_aliases_table.go b/roomserver/storage/postgres/room_aliases_table.go
index 031825fee..d13df8e7f 100644
--- a/roomserver/storage/postgres/room_aliases_table.go
+++ b/roomserver/storage/postgres/room_aliases_table.go
@@ -87,9 +87,10 @@ func (s *roomAliasesStatements) InsertRoomAlias(
 }
 
 func (s *roomAliasesStatements) SelectRoomIDFromAlias(
-	ctx context.Context, alias string,
+	ctx context.Context, txn *sql.Tx, alias string,
 ) (roomID string, err error) {
-	err = s.selectRoomIDFromAliasStmt.QueryRowContext(ctx, alias).Scan(&roomID)
+	stmt := sqlutil.TxStmt(txn, s.selectRoomIDFromAliasStmt)
+	err = stmt.QueryRowContext(ctx, alias).Scan(&roomID)
 	if err == sql.ErrNoRows {
 		return "", nil
 	}
@@ -97,9 +98,10 @@ func (s *roomAliasesStatements) SelectRoomIDFromAlias(
 }
 
 func (s *roomAliasesStatements) SelectAliasesFromRoomID(
-	ctx context.Context, roomID string,
+	ctx context.Context, txn *sql.Tx, roomID string,
 ) ([]string, error) {
-	rows, err := s.selectAliasesFromRoomIDStmt.QueryContext(ctx, roomID)
+	stmt := sqlutil.TxStmt(txn, s.selectAliasesFromRoomIDStmt)
+	rows, err := stmt.QueryContext(ctx, roomID)
 	if err != nil {
 		return nil, err
 	}
@@ -118,9 +120,10 @@ func (s *roomAliasesStatements) SelectAliasesFromRoomID(
 }
 
 func (s *roomAliasesStatements) SelectCreatorIDFromAlias(
-	ctx context.Context, alias string,
+	ctx context.Context, txn *sql.Tx, alias string,
 ) (creatorID string, err error) {
-	err = s.selectCreatorIDFromAliasStmt.QueryRowContext(ctx, alias).Scan(&creatorID)
+	stmt := sqlutil.TxStmt(txn, s.selectCreatorIDFromAliasStmt)
+	err = stmt.QueryRowContext(ctx, alias).Scan(&creatorID)
 	if err == sql.ErrNoRows {
 		return "", nil
 	}
diff --git a/roomserver/storage/postgres/rooms_table.go b/roomserver/storage/postgres/rooms_table.go
index f51eba4d4..b2685084d 100644
--- a/roomserver/storage/postgres/rooms_table.go
+++ b/roomserver/storage/postgres/rooms_table.go
@@ -117,8 +117,9 @@ func prepareRoomsTable(db *sql.DB) (tables.Rooms, error) {
 	}.Prepare(db)
 }
 
-func (s *roomStatements) SelectRoomIDs(ctx context.Context) ([]string, error) {
-	rows, err := s.selectRoomIDsStmt.QueryContext(ctx)
+func (s *roomStatements) SelectRoomIDs(ctx context.Context, txn *sql.Tx) ([]string, error) {
+	stmt := sqlutil.TxStmt(txn, s.selectRoomIDsStmt)
+	rows, err := stmt.QueryContext(ctx)
 	if err != nil {
 		return nil, err
 	}
@@ -143,10 +144,11 @@ func (s *roomStatements) InsertRoomNID(
 	return types.RoomNID(roomNID), err
 }
 
-func (s *roomStatements) SelectRoomInfo(ctx context.Context, roomID string) (*types.RoomInfo, error) {
+func (s *roomStatements) SelectRoomInfo(ctx context.Context, txn *sql.Tx, roomID string) (*types.RoomInfo, error) {
 	var info types.RoomInfo
 	var latestNIDs pq.Int64Array
-	err := s.selectRoomInfoStmt.QueryRowContext(ctx, roomID).Scan(
+	stmt := sqlutil.TxStmt(txn, s.selectRoomInfoStmt)
+	err := stmt.QueryRowContext(ctx, roomID).Scan(
 		&info.RoomVersion, &info.RoomNID, &info.StateSnapshotNID, &latestNIDs,
 	)
 	if err == sql.ErrNoRows {
@@ -170,7 +172,7 @@ func (s *roomStatements) SelectLatestEventNIDs(
 ) ([]types.EventNID, types.StateSnapshotNID, error) {
 	var nids pq.Int64Array
 	var stateSnapshotNID int64
-	stmt := s.selectLatestEventNIDsStmt
+	stmt := sqlutil.TxStmt(txn, s.selectLatestEventNIDsStmt)
 	err := stmt.QueryRowContext(ctx, int64(roomNID)).Scan(&nids, &stateSnapshotNID)
 	if err != nil {
 		return nil, 0, err
@@ -220,9 +222,10 @@ func (s *roomStatements) UpdateLatestEventNIDs(
 }
 
 func (s *roomStatements) SelectRoomVersionsForRoomNIDs(
-	ctx context.Context, roomNIDs []types.RoomNID,
+	ctx context.Context, txn *sql.Tx, roomNIDs []types.RoomNID,
 ) (map[types.RoomNID]gomatrixserverlib.RoomVersion, error) {
-	rows, err := s.selectRoomVersionsForRoomNIDsStmt.QueryContext(ctx, roomNIDsAsArray(roomNIDs))
+	stmt := sqlutil.TxStmt(txn, s.selectRoomVersionsForRoomNIDsStmt)
+	rows, err := stmt.QueryContext(ctx, roomNIDsAsArray(roomNIDs))
 	if err != nil {
 		return nil, err
 	}
@@ -239,12 +242,13 @@ func (s *roomStatements) SelectRoomVersionsForRoomNIDs(
 	return result, nil
 }
 
-func (s *roomStatements) BulkSelectRoomIDs(ctx context.Context, roomNIDs []types.RoomNID) ([]string, error) {
+func (s *roomStatements) BulkSelectRoomIDs(ctx context.Context, txn *sql.Tx, roomNIDs []types.RoomNID) ([]string, error) {
 	var array pq.Int64Array
 	for _, nid := range roomNIDs {
 		array = append(array, int64(nid))
 	}
-	rows, err := s.bulkSelectRoomIDsStmt.QueryContext(ctx, array)
+	stmt := sqlutil.TxStmt(txn, s.bulkSelectRoomIDsStmt)
+	rows, err := stmt.QueryContext(ctx, array)
 	if err != nil {
 		return nil, err
 	}
@@ -260,12 +264,13 @@ func (s *roomStatements) BulkSelectRoomIDs(ctx context.Context, roomNIDs []types
 	return roomIDs, nil
 }
 
-func (s *roomStatements) BulkSelectRoomNIDs(ctx context.Context, roomIDs []string) ([]types.RoomNID, error) {
+func (s *roomStatements) BulkSelectRoomNIDs(ctx context.Context, txn *sql.Tx, roomIDs []string) ([]types.RoomNID, error) {
 	var array pq.StringArray
 	for _, roomID := range roomIDs {
 		array = append(array, roomID)
 	}
-	rows, err := s.bulkSelectRoomNIDsStmt.QueryContext(ctx, array)
+	stmt := sqlutil.TxStmt(txn, s.bulkSelectRoomNIDsStmt)
+	rows, err := stmt.QueryContext(ctx, array)
 	if err != nil {
 		return nil, err
 	}
diff --git a/roomserver/storage/postgres/state_block_table.go b/roomserver/storage/postgres/state_block_table.go
index 27d85e83b..6f8f9e1b5 100644
--- a/roomserver/storage/postgres/state_block_table.go
+++ b/roomserver/storage/postgres/state_block_table.go
@@ -86,8 +86,7 @@ func prepareStateBlockTable(db *sql.DB) (tables.StateBlock, error) {
 }
 
 func (s *stateBlockStatements) BulkInsertStateData(
-	ctx context.Context,
-	txn *sql.Tx,
+	ctx context.Context, txn *sql.Tx,
 	entries types.StateEntries,
 ) (id types.StateBlockNID, err error) {
 	entries = entries[:util.SortAndUnique(entries)]
@@ -95,16 +94,18 @@ func (s *stateBlockStatements) BulkInsertStateData(
 	for _, e := range entries {
 		nids = append(nids, e.EventNID)
 	}
-	err = s.insertStateDataStmt.QueryRowContext(
+	stmt := sqlutil.TxStmt(txn, s.insertStateDataStmt)
+	err = stmt.QueryRowContext(
 		ctx, nids.Hash(), eventNIDsAsArray(nids),
 	).Scan(&id)
 	return
 }
 
 func (s *stateBlockStatements) BulkSelectStateBlockEntries(
-	ctx context.Context, stateBlockNIDs types.StateBlockNIDs,
+	ctx context.Context, txn *sql.Tx, stateBlockNIDs types.StateBlockNIDs,
 ) ([][]types.EventNID, error) {
-	rows, err := s.bulkSelectStateBlockEntriesStmt.QueryContext(ctx, stateBlockNIDsAsArray(stateBlockNIDs))
+	stmt := sqlutil.TxStmt(txn, s.bulkSelectStateBlockEntriesStmt)
+	rows, err := stmt.QueryContext(ctx, stateBlockNIDsAsArray(stateBlockNIDs))
 	if err != nil {
 		return nil, err
 	}
diff --git a/roomserver/storage/postgres/state_snapshot_table.go b/roomserver/storage/postgres/state_snapshot_table.go
index 4fc0fa48a..ce9f24636 100644
--- a/roomserver/storage/postgres/state_snapshot_table.go
+++ b/roomserver/storage/postgres/state_snapshot_table.go
@@ -105,13 +105,14 @@ func (s *stateSnapshotStatements) InsertState(
 }
 
 func (s *stateSnapshotStatements) BulkSelectStateBlockNIDs(
-	ctx context.Context, stateNIDs []types.StateSnapshotNID,
+	ctx context.Context, txn *sql.Tx, stateNIDs []types.StateSnapshotNID,
 ) ([]types.StateBlockNIDList, error) {
 	nids := make([]int64, len(stateNIDs))
 	for i := range stateNIDs {
 		nids[i] = int64(stateNIDs[i])
 	}
-	rows, err := s.bulkSelectStateBlockNIDsStmt.QueryContext(ctx, pq.Int64Array(nids))
+	stmt := sqlutil.TxStmt(txn, s.bulkSelectStateBlockNIDsStmt)
+	rows, err := stmt.QueryContext(ctx, pq.Int64Array(nids))
 	if err != nil {
 		return nil, err
 	}
diff --git a/roomserver/storage/shared/latest_events_updater.go b/roomserver/storage/shared/latest_events_updater.go
deleted file mode 100644
index 36865081a..000000000
--- a/roomserver/storage/shared/latest_events_updater.go
+++ /dev/null
@@ -1,133 +0,0 @@
-package shared
-
-import (
-	"context"
-	"database/sql"
-	"fmt"
-
-	"github.com/matrix-org/dendrite/roomserver/types"
-	"github.com/matrix-org/gomatrixserverlib"
-)
-
-type LatestEventsUpdater struct {
-	transaction
-	d                       *Database
-	roomInfo                types.RoomInfo
-	latestEvents            []types.StateAtEventAndReference
-	lastEventIDSent         string
-	currentStateSnapshotNID types.StateSnapshotNID
-}
-
-func rollback(txn *sql.Tx) {
-	if txn == nil {
-		return
-	}
-	txn.Rollback() // nolint: errcheck
-}
-
-func NewLatestEventsUpdater(ctx context.Context, d *Database, txn *sql.Tx, roomInfo types.RoomInfo) (*LatestEventsUpdater, error) {
-	eventNIDs, lastEventNIDSent, currentStateSnapshotNID, err :=
-		d.RoomsTable.SelectLatestEventsNIDsForUpdate(ctx, txn, roomInfo.RoomNID)
-	if err != nil {
-		rollback(txn)
-		return nil, err
-	}
-	stateAndRefs, err := d.EventsTable.BulkSelectStateAtEventAndReference(ctx, txn, eventNIDs)
-	if err != nil {
-		rollback(txn)
-		return nil, err
-	}
-	var lastEventIDSent string
-	if lastEventNIDSent != 0 {
-		lastEventIDSent, err = d.EventsTable.SelectEventID(ctx, txn, lastEventNIDSent)
-		if err != nil {
-			rollback(txn)
-			return nil, err
-		}
-	}
-	return &LatestEventsUpdater{
-		transaction{ctx, txn}, d, roomInfo, stateAndRefs, lastEventIDSent, currentStateSnapshotNID,
-	}, nil
-}
-
-// RoomVersion implements types.RoomRecentEventsUpdater
-func (u *LatestEventsUpdater) RoomVersion() (version gomatrixserverlib.RoomVersion) {
-	return u.roomInfo.RoomVersion
-}
-
-// LatestEvents implements types.RoomRecentEventsUpdater
-func (u *LatestEventsUpdater) LatestEvents() []types.StateAtEventAndReference {
-	return u.latestEvents
-}
-
-// LastEventIDSent implements types.RoomRecentEventsUpdater
-func (u *LatestEventsUpdater) LastEventIDSent() string {
-	return u.lastEventIDSent
-}
-
-// CurrentStateSnapshotNID implements types.RoomRecentEventsUpdater
-func (u *LatestEventsUpdater) CurrentStateSnapshotNID() types.StateSnapshotNID {
-	return u.currentStateSnapshotNID
-}
-
-// StorePreviousEvents implements types.RoomRecentEventsUpdater - This must be called from a Writer
-func (u *LatestEventsUpdater) StorePreviousEvents(eventNID types.EventNID, previousEventReferences []gomatrixserverlib.EventReference) error {
-	for _, ref := range previousEventReferences {
-		if err := u.d.PrevEventsTable.InsertPreviousEvent(u.ctx, u.txn, ref.EventID, ref.EventSHA256, eventNID); err != nil {
-			return fmt.Errorf("u.d.PrevEventsTable.InsertPreviousEvent: %w", err)
-		}
-	}
-	return nil
-}
-
-// IsReferenced implements types.RoomRecentEventsUpdater
-func (u *LatestEventsUpdater) IsReferenced(eventReference gomatrixserverlib.EventReference) (bool, error) {
-	err := u.d.PrevEventsTable.SelectPreviousEventExists(u.ctx, u.txn, eventReference.EventID, eventReference.EventSHA256)
-	if err == nil {
-		return true, nil
-	}
-	if err == sql.ErrNoRows {
-		return false, nil
-	}
-	return false, fmt.Errorf("u.d.PrevEventsTable.SelectPreviousEventExists: %w", err)
-}
-
-// SetLatestEvents implements types.RoomRecentEventsUpdater
-func (u *LatestEventsUpdater) SetLatestEvents(
-	roomNID types.RoomNID, latest []types.StateAtEventAndReference, lastEventNIDSent types.EventNID,
-	currentStateSnapshotNID types.StateSnapshotNID,
-) error {
-	eventNIDs := make([]types.EventNID, len(latest))
-	for i := range latest {
-		eventNIDs[i] = latest[i].EventNID
-	}
-	return u.d.Writer.Do(u.d.DB, u.txn, func(txn *sql.Tx) error {
-		if err := u.d.RoomsTable.UpdateLatestEventNIDs(u.ctx, txn, roomNID, eventNIDs, lastEventNIDSent, currentStateSnapshotNID); err != nil {
-			return fmt.Errorf("u.d.RoomsTable.updateLatestEventNIDs: %w", err)
-		}
-		if roomID, ok := u.d.Cache.GetRoomServerRoomID(roomNID); ok {
-			if roomInfo, ok := u.d.Cache.GetRoomInfo(roomID); ok {
-				roomInfo.StateSnapshotNID = currentStateSnapshotNID
-				roomInfo.IsStub = false
-				u.d.Cache.StoreRoomInfo(roomID, roomInfo)
-			}
-		}
-		return nil
-	})
-}
-
-// HasEventBeenSent implements types.RoomRecentEventsUpdater
-func (u *LatestEventsUpdater) HasEventBeenSent(eventNID types.EventNID) (bool, error) {
-	return u.d.EventsTable.SelectEventSentToOutput(u.ctx, u.txn, eventNID)
-}
-
-// MarkEventAsSent implements types.RoomRecentEventsUpdater
-func (u *LatestEventsUpdater) MarkEventAsSent(eventNID types.EventNID) error {
-	return u.d.Writer.Do(u.d.DB, u.txn, func(txn *sql.Tx) error {
-		return u.d.EventsTable.UpdateEventSentToOutput(u.ctx, txn, eventNID)
-	})
-}
-
-func (u *LatestEventsUpdater) MembershipUpdater(targetUserNID types.EventStateKeyNID, targetLocal bool) (*MembershipUpdater, error) {
-	return u.d.membershipUpdaterTxn(u.ctx, u.txn, u.roomInfo.RoomNID, targetUserNID, targetLocal)
-}
diff --git a/roomserver/storage/shared/room_updater.go b/roomserver/storage/shared/room_updater.go
new file mode 100644
index 000000000..bb9f5dc62
--- /dev/null
+++ b/roomserver/storage/shared/room_updater.go
@@ -0,0 +1,262 @@
+package shared
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+
+	"github.com/matrix-org/dendrite/roomserver/types"
+	"github.com/matrix-org/gomatrixserverlib"
+)
+
+type RoomUpdater struct {
+	transaction
+	d                       *Database
+	roomInfo                *types.RoomInfo
+	latestEvents            []types.StateAtEventAndReference
+	lastEventIDSent         string
+	currentStateSnapshotNID types.StateSnapshotNID
+}
+
+func rollback(txn *sql.Tx) {
+	if txn == nil {
+		return
+	}
+	txn.Rollback() // nolint: errcheck
+}
+
+func NewRoomUpdater(ctx context.Context, d *Database, txn *sql.Tx, roomInfo *types.RoomInfo) (*RoomUpdater, error) {
+	// If the roomInfo is nil then that means that the room doesn't exist
+	// yet, so we can't do `SelectLatestEventsNIDsForUpdate` because that
+	// would involve locking a row on the table that doesn't exist. Instead
+	// we will just run with a normal database transaction. It'll either
+	// succeed, processing a create event which creates the room, or it won't.
+	if roomInfo == nil {
+		return &RoomUpdater{
+			transaction{ctx, txn}, d, nil, nil, "", 0,
+		}, nil
+	}
+
+	eventNIDs, lastEventNIDSent, currentStateSnapshotNID, err :=
+		d.RoomsTable.SelectLatestEventsNIDsForUpdate(ctx, txn, roomInfo.RoomNID)
+	if err != nil {
+		rollback(txn)
+		return nil, err
+	}
+	stateAndRefs, err := d.EventsTable.BulkSelectStateAtEventAndReference(ctx, txn, eventNIDs)
+	if err != nil {
+		rollback(txn)
+		return nil, err
+	}
+	var lastEventIDSent string
+	if lastEventNIDSent != 0 {
+		lastEventIDSent, err = d.EventsTable.SelectEventID(ctx, txn, lastEventNIDSent)
+		if err != nil {
+			rollback(txn)
+			return nil, err
+		}
+	}
+	return &RoomUpdater{
+		transaction{ctx, txn}, d, roomInfo, stateAndRefs, lastEventIDSent, currentStateSnapshotNID,
+	}, nil
+}
+
+// Implements sqlutil.Transaction
+func (u *RoomUpdater) Commit() error {
+	if u.txn == nil { // SQLite mode probably
+		return nil
+	}
+	return u.txn.Commit()
+}
+
+// Implements sqlutil.Transaction
+func (u *RoomUpdater) Rollback() error {
+	if u.txn == nil { // SQLite mode probably
+		return nil
+	}
+	return u.txn.Rollback()
+}
+
+// RoomVersion implements types.RoomRecentEventsUpdater
+func (u *RoomUpdater) RoomVersion() (version gomatrixserverlib.RoomVersion) {
+	return u.roomInfo.RoomVersion
+}
+
+// LatestEvents implements types.RoomRecentEventsUpdater
+func (u *RoomUpdater) LatestEvents() []types.StateAtEventAndReference {
+	return u.latestEvents
+}
+
+// LastEventIDSent implements types.RoomRecentEventsUpdater
+func (u *RoomUpdater) LastEventIDSent() string {
+	return u.lastEventIDSent
+}
+
+// CurrentStateSnapshotNID implements types.RoomRecentEventsUpdater
+func (u *RoomUpdater) CurrentStateSnapshotNID() types.StateSnapshotNID {
+	return u.currentStateSnapshotNID
+}
+
+// StorePreviousEvents implements types.RoomRecentEventsUpdater - This must be called from a Writer
+func (u *RoomUpdater) StorePreviousEvents(eventNID types.EventNID, previousEventReferences []gomatrixserverlib.EventReference) error {
+	return u.d.Writer.Do(u.d.DB, u.txn, func(txn *sql.Tx) error {
+		for _, ref := range previousEventReferences {
+			if err := u.d.PrevEventsTable.InsertPreviousEvent(u.ctx, txn, ref.EventID, ref.EventSHA256, eventNID); err != nil {
+				return fmt.Errorf("u.d.PrevEventsTable.InsertPreviousEvent: %w", err)
+			}
+		}
+		return nil
+	})
+}
+
+func (u *RoomUpdater) Events(
+	ctx context.Context, eventNIDs []types.EventNID,
+) ([]types.Event, error) {
+	return u.d.events(ctx, u.txn, eventNIDs)
+}
+
+func (u *RoomUpdater) SnapshotNIDFromEventID(
+	ctx context.Context, eventID string,
+) (types.StateSnapshotNID, error) {
+	return u.d.snapshotNIDFromEventID(ctx, u.txn, eventID)
+}
+
+func (u *RoomUpdater) StoreEvent(
+	ctx context.Context, event *gomatrixserverlib.Event,
+	authEventNIDs []types.EventNID, isRejected bool,
+) (types.EventNID, types.RoomNID, types.StateAtEvent, *gomatrixserverlib.Event, string, error) {
+	return u.d.storeEvent(ctx, u, event, authEventNIDs, isRejected)
+}
+
+func (u *RoomUpdater) StateBlockNIDs(
+	ctx context.Context, stateNIDs []types.StateSnapshotNID,
+) ([]types.StateBlockNIDList, error) {
+	return u.d.stateBlockNIDs(ctx, u.txn, stateNIDs)
+}
+
+func (u *RoomUpdater) StateEntries(
+	ctx context.Context, stateBlockNIDs []types.StateBlockNID,
+) ([]types.StateEntryList, error) {
+	return u.d.stateEntries(ctx, u.txn, stateBlockNIDs)
+}
+
+func (u *RoomUpdater) StateEntriesForTuples(
+	ctx context.Context,
+	stateBlockNIDs []types.StateBlockNID,
+	stateKeyTuples []types.StateKeyTuple,
+) ([]types.StateEntryList, error) {
+	return u.d.stateEntriesForTuples(ctx, u.txn, stateBlockNIDs, stateKeyTuples)
+}
+
+func (u *RoomUpdater) AddState(
+	ctx context.Context,
+	roomNID types.RoomNID,
+	stateBlockNIDs []types.StateBlockNID,
+	state []types.StateEntry,
+) (stateNID types.StateSnapshotNID, err error) {
+	return u.d.addState(ctx, u.txn, roomNID, stateBlockNIDs, state)
+}
+
+func (u *RoomUpdater) SetState(
+	ctx context.Context, eventNID types.EventNID, stateNID types.StateSnapshotNID,
+) error {
+	return u.d.Writer.Do(u.d.DB, u.txn, func(txn *sql.Tx) error {
+		return u.d.EventsTable.UpdateEventState(ctx, txn, eventNID, stateNID)
+	})
+}
+
+func (u *RoomUpdater) EventTypeNIDs(
+	ctx context.Context, eventTypes []string,
+) (map[string]types.EventTypeNID, error) {
+	return u.d.eventTypeNIDs(ctx, u.txn, eventTypes)
+}
+
+func (u *RoomUpdater) EventStateKeyNIDs(
+	ctx context.Context, eventStateKeys []string,
+) (map[string]types.EventStateKeyNID, error) {
+	return u.d.eventStateKeyNIDs(ctx, u.txn, eventStateKeys)
+}
+
+func (u *RoomUpdater) RoomInfo(ctx context.Context, roomID string) (*types.RoomInfo, error) {
+	return u.d.roomInfo(ctx, u.txn, roomID)
+}
+
+func (u *RoomUpdater) EventIDs(
+	ctx context.Context, eventNIDs []types.EventNID,
+) (map[types.EventNID]string, error) {
+	return u.d.EventsTable.BulkSelectEventID(ctx, u.txn, eventNIDs)
+}
+
+func (u *RoomUpdater) StateAtEventIDs(
+	ctx context.Context, eventIDs []string,
+) ([]types.StateAtEvent, error) {
+	return u.d.EventsTable.BulkSelectStateAtEventByID(ctx, u.txn, eventIDs)
+}
+
+func (u *RoomUpdater) StateEntriesForEventIDs(
+	ctx context.Context, eventIDs []string,
+) ([]types.StateEntry, error) {
+	return u.d.EventsTable.BulkSelectStateEventByID(ctx, u.txn, eventIDs)
+}
+
+func (u *RoomUpdater) EventsFromIDs(ctx context.Context, eventIDs []string) ([]types.Event, error) {
+	return u.d.eventsFromIDs(ctx, u.txn, eventIDs)
+}
+
+func (u *RoomUpdater) GetMembershipEventNIDsForRoom(
+	ctx context.Context, roomNID types.RoomNID, joinOnly bool, localOnly bool,
+) ([]types.EventNID, error) {
+	return u.d.getMembershipEventNIDsForRoom(ctx, u.txn, roomNID, joinOnly, localOnly)
+}
+
+// IsReferenced implements types.RoomRecentEventsUpdater
+func (u *RoomUpdater) IsReferenced(eventReference gomatrixserverlib.EventReference) (bool, error) {
+	err := u.d.PrevEventsTable.SelectPreviousEventExists(u.ctx, u.txn, eventReference.EventID, eventReference.EventSHA256)
+	if err == nil {
+		return true, nil
+	}
+	if err == sql.ErrNoRows {
+		return false, nil
+	}
+	return false, fmt.Errorf("u.d.PrevEventsTable.SelectPreviousEventExists: %w", err)
+}
+
+// SetLatestEvents implements types.RoomRecentEventsUpdater
+func (u *RoomUpdater) SetLatestEvents(
+	roomNID types.RoomNID, latest []types.StateAtEventAndReference, lastEventNIDSent types.EventNID,
+	currentStateSnapshotNID types.StateSnapshotNID,
+) error {
+	eventNIDs := make([]types.EventNID, len(latest))
+	for i := range latest {
+		eventNIDs[i] = latest[i].EventNID
+	}
+	return u.d.Writer.Do(u.d.DB, u.txn, func(txn *sql.Tx) error {
+		if err := u.d.RoomsTable.UpdateLatestEventNIDs(u.ctx, txn, roomNID, eventNIDs, lastEventNIDSent, currentStateSnapshotNID); err != nil {
+			return fmt.Errorf("u.d.RoomsTable.updateLatestEventNIDs: %w", err)
+		}
+		if roomID, ok := u.d.Cache.GetRoomServerRoomID(roomNID); ok {
+			if roomInfo, ok := u.d.Cache.GetRoomInfo(roomID); ok {
+				roomInfo.StateSnapshotNID = currentStateSnapshotNID
+				roomInfo.IsStub = false
+				u.d.Cache.StoreRoomInfo(roomID, roomInfo)
+			}
+		}
+		return nil
+	})
+}
+
+// HasEventBeenSent implements types.RoomRecentEventsUpdater
+func (u *RoomUpdater) HasEventBeenSent(eventNID types.EventNID) (bool, error) {
+	return u.d.EventsTable.SelectEventSentToOutput(u.ctx, u.txn, eventNID)
+}
+
+// MarkEventAsSent implements types.RoomRecentEventsUpdater
+func (u *RoomUpdater) MarkEventAsSent(eventNID types.EventNID) error {
+	return u.d.Writer.Do(u.d.DB, u.txn, func(txn *sql.Tx) error {
+		return u.d.EventsTable.UpdateEventSentToOutput(u.ctx, txn, eventNID)
+	})
+}
+
+func (u *RoomUpdater) MembershipUpdater(targetUserNID types.EventStateKeyNID, targetLocal bool) (*MembershipUpdater, error) {
+	return u.d.membershipUpdaterTxn(u.ctx, u.txn, u.roomInfo.RoomNID, targetUserNID, targetLocal)
+}
diff --git a/roomserver/storage/shared/storage.go b/roomserver/storage/shared/storage.go
index d4c5ebb5b..127cd1f52 100644
--- a/roomserver/storage/shared/storage.go
+++ b/roomserver/storage/shared/storage.go
@@ -26,23 +26,23 @@ import (
 const redactionsArePermanent = true
 
 type Database struct {
-	DB                         *sql.DB
-	Cache                      caching.RoomServerCaches
-	Writer                     sqlutil.Writer
-	EventsTable                tables.Events
-	EventJSONTable             tables.EventJSON
-	EventTypesTable            tables.EventTypes
-	EventStateKeysTable        tables.EventStateKeys
-	RoomsTable                 tables.Rooms
-	StateSnapshotTable         tables.StateSnapshot
-	StateBlockTable            tables.StateBlock
-	RoomAliasesTable           tables.RoomAliases
-	PrevEventsTable            tables.PreviousEvents
-	InvitesTable               tables.Invites
-	MembershipTable            tables.Membership
-	PublishedTable             tables.Published
-	RedactionsTable            tables.Redactions
-	GetLatestEventsForUpdateFn func(ctx context.Context, roomInfo types.RoomInfo) (*LatestEventsUpdater, error)
+	DB                  *sql.DB
+	Cache               caching.RoomServerCaches
+	Writer              sqlutil.Writer
+	EventsTable         tables.Events
+	EventJSONTable      tables.EventJSON
+	EventTypesTable     tables.EventTypes
+	EventStateKeysTable tables.EventStateKeys
+	RoomsTable          tables.Rooms
+	StateSnapshotTable  tables.StateSnapshot
+	StateBlockTable     tables.StateBlock
+	RoomAliasesTable    tables.RoomAliases
+	PrevEventsTable     tables.PreviousEvents
+	InvitesTable        tables.Invites
+	MembershipTable     tables.Membership
+	PublishedTable      tables.Published
+	RedactionsTable     tables.Redactions
+	GetRoomUpdaterFn    func(ctx context.Context, roomInfo *types.RoomInfo) (*RoomUpdater, error)
 }
 
 func (d *Database) SupportsConcurrentRoomInputs() bool {
@@ -51,6 +51,12 @@ func (d *Database) SupportsConcurrentRoomInputs() bool {
 
 func (d *Database) EventTypeNIDs(
 	ctx context.Context, eventTypes []string,
+) (map[string]types.EventTypeNID, error) {
+	return d.eventTypeNIDs(ctx, nil, eventTypes)
+}
+
+func (d *Database) eventTypeNIDs(
+	ctx context.Context, txn *sql.Tx, eventTypes []string,
 ) (map[string]types.EventTypeNID, error) {
 	result := make(map[string]types.EventTypeNID)
 	remaining := []string{}
@@ -62,7 +68,7 @@ func (d *Database) EventTypeNIDs(
 		}
 	}
 	if len(remaining) > 0 {
-		nids, err := d.EventTypesTable.BulkSelectEventTypeNID(ctx, remaining)
+		nids, err := d.EventTypesTable.BulkSelectEventTypeNID(ctx, txn, remaining)
 		if err != nil {
 			return nil, err
 		}
@@ -77,11 +83,17 @@ func (d *Database) EventTypeNIDs(
 func (d *Database) EventStateKeys(
 	ctx context.Context, eventStateKeyNIDs []types.EventStateKeyNID,
 ) (map[types.EventStateKeyNID]string, error) {
-	return d.EventStateKeysTable.BulkSelectEventStateKey(ctx, eventStateKeyNIDs)
+	return d.EventStateKeysTable.BulkSelectEventStateKey(ctx, nil, eventStateKeyNIDs)
 }
 
 func (d *Database) EventStateKeyNIDs(
 	ctx context.Context, eventStateKeys []string,
+) (map[string]types.EventStateKeyNID, error) {
+	return d.eventStateKeyNIDs(ctx, nil, eventStateKeys)
+}
+
+func (d *Database) eventStateKeyNIDs(
+	ctx context.Context, txn *sql.Tx, eventStateKeys []string,
 ) (map[string]types.EventStateKeyNID, error) {
 	result := make(map[string]types.EventStateKeyNID)
 	remaining := []string{}
@@ -93,7 +105,7 @@ func (d *Database) EventStateKeyNIDs(
 		}
 	}
 	if len(remaining) > 0 {
-		nids, err := d.EventStateKeysTable.BulkSelectEventStateKeyNID(ctx, remaining)
+		nids, err := d.EventStateKeysTable.BulkSelectEventStateKeyNID(ctx, txn, remaining)
 		if err != nil {
 			return nil, err
 		}
@@ -108,23 +120,31 @@ func (d *Database) EventStateKeyNIDs(
 func (d *Database) StateEntriesForEventIDs(
 	ctx context.Context, eventIDs []string,
 ) ([]types.StateEntry, error) {
-	return d.EventsTable.BulkSelectStateEventByID(ctx, eventIDs)
+	return d.EventsTable.BulkSelectStateEventByID(ctx, nil, eventIDs)
 }
 
 func (d *Database) StateEntriesForTuples(
 	ctx context.Context,
 	stateBlockNIDs []types.StateBlockNID,
 	stateKeyTuples []types.StateKeyTuple,
+) ([]types.StateEntryList, error) {
+	return d.stateEntriesForTuples(ctx, nil, stateBlockNIDs, stateKeyTuples)
+}
+
+func (d *Database) stateEntriesForTuples(
+	ctx context.Context, txn *sql.Tx,
+	stateBlockNIDs []types.StateBlockNID,
+	stateKeyTuples []types.StateKeyTuple,
 ) ([]types.StateEntryList, error) {
 	entries, err := d.StateBlockTable.BulkSelectStateBlockEntries(
-		ctx, stateBlockNIDs,
+		ctx, txn, stateBlockNIDs,
 	)
 	if err != nil {
 		return nil, fmt.Errorf("d.StateBlockTable.BulkSelectStateBlockEntries: %w", err)
 	}
 	lists := []types.StateEntryList{}
 	for i, entry := range entries {
-		entries, err := d.EventsTable.BulkSelectStateEventByNID(ctx, entry, stateKeyTuples)
+		entries, err := d.EventsTable.BulkSelectStateEventByNID(ctx, txn, entry, stateKeyTuples)
 		if err != nil {
 			return nil, fmt.Errorf("d.EventsTable.BulkSelectStateEventByNID: %w", err)
 		}
@@ -137,10 +157,14 @@ func (d *Database) StateEntriesForTuples(
 }
 
 func (d *Database) RoomInfo(ctx context.Context, roomID string) (*types.RoomInfo, error) {
+	return d.roomInfo(ctx, nil, roomID)
+}
+
+func (d *Database) roomInfo(ctx context.Context, txn *sql.Tx, roomID string) (*types.RoomInfo, error) {
 	if roomInfo, ok := d.Cache.GetRoomInfo(roomID); ok {
 		return &roomInfo, nil
 	}
-	roomInfo, err := d.RoomsTable.SelectRoomInfo(ctx, roomID)
+	roomInfo, err := d.RoomsTable.SelectRoomInfo(ctx, txn, roomID)
 	if err == nil && roomInfo != nil {
 		d.Cache.StoreRoomServerRoomID(roomInfo.RoomNID, roomID)
 		d.Cache.StoreRoomInfo(roomID, *roomInfo)
@@ -153,13 +177,22 @@ func (d *Database) AddState(
 	roomNID types.RoomNID,
 	stateBlockNIDs []types.StateBlockNID,
 	state []types.StateEntry,
+) (stateNID types.StateSnapshotNID, err error) {
+	return d.addState(ctx, nil, roomNID, stateBlockNIDs, state)
+}
+
+func (d *Database) addState(
+	ctx context.Context, txn *sql.Tx,
+	roomNID types.RoomNID,
+	stateBlockNIDs []types.StateBlockNID,
+	state []types.StateEntry,
 ) (stateNID types.StateSnapshotNID, err error) {
 	if len(stateBlockNIDs) > 0 && len(state) > 0 {
 		// Check to see if the event already appears in any of the existing state
 		// blocks. If it does then we should not add it again, as this will just
 		// result in excess state blocks and snapshots.
 		// TODO: Investigate why this is happening - probably input_events.go!
-		blocks, berr := d.StateBlockTable.BulkSelectStateBlockEntries(ctx, stateBlockNIDs)
+		blocks, berr := d.StateBlockTable.BulkSelectStateBlockEntries(ctx, txn, stateBlockNIDs)
 		if berr != nil {
 			return 0, fmt.Errorf("d.StateBlockTable.BulkSelectStateBlockEntries: %w", berr)
 		}
@@ -180,7 +213,7 @@ func (d *Database) AddState(
 			}
 		}
 	}
-	err = d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
+	err = d.Writer.Do(d.DB, txn, func(txn *sql.Tx) error {
 		if len(state) > 0 {
 			// If there's any state left to add then let's add new blocks.
 			var stateBlockNID types.StateBlockNID
@@ -205,7 +238,13 @@ func (d *Database) AddState(
 func (d *Database) EventNIDs(
 	ctx context.Context, eventIDs []string,
 ) (map[string]types.EventNID, error) {
-	return d.EventsTable.BulkSelectEventNID(ctx, eventIDs)
+	return d.eventNIDs(ctx, nil, eventIDs)
+}
+
+func (d *Database) eventNIDs(
+	ctx context.Context, txn *sql.Tx, eventIDs []string,
+) (map[string]types.EventNID, error) {
+	return d.EventsTable.BulkSelectEventNID(ctx, txn, eventIDs)
 }
 
 func (d *Database) SetState(
@@ -219,24 +258,34 @@ func (d *Database) SetState(
 func (d *Database) StateAtEventIDs(
 	ctx context.Context, eventIDs []string,
 ) ([]types.StateAtEvent, error) {
-	return d.EventsTable.BulkSelectStateAtEventByID(ctx, eventIDs)
+	return d.EventsTable.BulkSelectStateAtEventByID(ctx, nil, eventIDs)
 }
 
 func (d *Database) SnapshotNIDFromEventID(
 	ctx context.Context, eventID string,
 ) (types.StateSnapshotNID, error) {
-	_, stateNID, err := d.EventsTable.SelectEvent(ctx, nil, eventID)
+	return d.snapshotNIDFromEventID(ctx, nil, eventID)
+}
+
+func (d *Database) snapshotNIDFromEventID(
+	ctx context.Context, txn *sql.Tx, eventID string,
+) (types.StateSnapshotNID, error) {
+	_, stateNID, err := d.EventsTable.SelectEvent(ctx, txn, eventID)
 	return stateNID, err
 }
 
 func (d *Database) EventIDs(
 	ctx context.Context, eventNIDs []types.EventNID,
 ) (map[types.EventNID]string, error) {
-	return d.EventsTable.BulkSelectEventID(ctx, eventNIDs)
+	return d.EventsTable.BulkSelectEventID(ctx, nil, eventNIDs)
 }
 
 func (d *Database) EventsFromIDs(ctx context.Context, eventIDs []string) ([]types.Event, error) {
-	nidMap, err := d.EventNIDs(ctx, eventIDs)
+	return d.eventsFromIDs(ctx, nil, eventIDs)
+}
+
+func (d *Database) eventsFromIDs(ctx context.Context, txn *sql.Tx, eventIDs []string) ([]types.Event, error) {
+	nidMap, err := d.eventNIDs(ctx, txn, eventIDs)
 	if err != nil {
 		return nil, err
 	}
@@ -246,7 +295,7 @@ func (d *Database) EventsFromIDs(ctx context.Context, eventIDs []string) ([]type
 		nids = append(nids, nid)
 	}
 
-	return d.Events(ctx, nids)
+	return d.events(ctx, txn, nids)
 }
 
 func (d *Database) LatestEventIDs(
@@ -271,21 +320,33 @@ func (d *Database) LatestEventIDs(
 func (d *Database) StateBlockNIDs(
 	ctx context.Context, stateNIDs []types.StateSnapshotNID,
 ) ([]types.StateBlockNIDList, error) {
-	return d.StateSnapshotTable.BulkSelectStateBlockNIDs(ctx, stateNIDs)
+	return d.stateBlockNIDs(ctx, nil, stateNIDs)
+}
+
+func (d *Database) stateBlockNIDs(
+	ctx context.Context, txn *sql.Tx, stateNIDs []types.StateSnapshotNID,
+) ([]types.StateBlockNIDList, error) {
+	return d.StateSnapshotTable.BulkSelectStateBlockNIDs(ctx, txn, stateNIDs)
 }
 
 func (d *Database) StateEntries(
 	ctx context.Context, stateBlockNIDs []types.StateBlockNID,
+) ([]types.StateEntryList, error) {
+	return d.stateEntries(ctx, nil, stateBlockNIDs)
+}
+
+func (d *Database) stateEntries(
+	ctx context.Context, txn *sql.Tx, stateBlockNIDs []types.StateBlockNID,
 ) ([]types.StateEntryList, error) {
 	entries, err := d.StateBlockTable.BulkSelectStateBlockEntries(
-		ctx, stateBlockNIDs,
+		ctx, txn, stateBlockNIDs,
 	)
 	if err != nil {
 		return nil, fmt.Errorf("d.StateBlockTable.BulkSelectStateBlockEntries: %w", err)
 	}
 	lists := make([]types.StateEntryList, 0, len(entries))
 	for i, entry := range entries {
-		eventNIDs, err := d.EventsTable.BulkSelectStateEventByNID(ctx, entry, nil)
+		eventNIDs, err := d.EventsTable.BulkSelectStateEventByNID(ctx, txn, entry, nil)
 		if err != nil {
 			return nil, fmt.Errorf("d.EventsTable.BulkSelectStateEventByNID: %w", err)
 		}
@@ -304,17 +365,17 @@ func (d *Database) SetRoomAlias(ctx context.Context, alias string, roomID string
 }
 
 func (d *Database) GetRoomIDForAlias(ctx context.Context, alias string) (string, error) {
-	return d.RoomAliasesTable.SelectRoomIDFromAlias(ctx, alias)
+	return d.RoomAliasesTable.SelectRoomIDFromAlias(ctx, nil, alias)
 }
 
 func (d *Database) GetAliasesForRoomID(ctx context.Context, roomID string) ([]string, error) {
-	return d.RoomAliasesTable.SelectAliasesFromRoomID(ctx, roomID)
+	return d.RoomAliasesTable.SelectAliasesFromRoomID(ctx, nil, roomID)
 }
 
 func (d *Database) GetCreatorIDForAlias(
 	ctx context.Context, alias string,
 ) (string, error) {
-	return d.RoomAliasesTable.SelectCreatorIDFromAlias(ctx, alias)
+	return d.RoomAliasesTable.SelectCreatorIDFromAlias(ctx, nil, alias)
 }
 
 func (d *Database) RemoveRoomAlias(ctx context.Context, alias string) error {
@@ -335,7 +396,7 @@ func (d *Database) GetMembership(ctx context.Context, roomNID types.RoomNID, req
 
 	senderMembershipEventNID, senderMembership, isRoomforgotten, err :=
 		d.MembershipTable.SelectMembershipFromRoomAndTarget(
-			ctx, roomNID, requestSenderUserNID,
+			ctx, nil, roomNID, requestSenderUserNID,
 		)
 	if err == sql.ErrNoRows {
 		// The user has never been a member of that room
@@ -349,14 +410,20 @@ func (d *Database) GetMembership(ctx context.Context, roomNID types.RoomNID, req
 
 func (d *Database) GetMembershipEventNIDsForRoom(
 	ctx context.Context, roomNID types.RoomNID, joinOnly bool, localOnly bool,
+) ([]types.EventNID, error) {
+	return d.getMembershipEventNIDsForRoom(ctx, nil, roomNID, joinOnly, localOnly)
+}
+
+func (d *Database) getMembershipEventNIDsForRoom(
+	ctx context.Context, txn *sql.Tx, roomNID types.RoomNID, joinOnly bool, localOnly bool,
 ) ([]types.EventNID, error) {
 	if joinOnly {
 		return d.MembershipTable.SelectMembershipsFromRoomAndMembership(
-			ctx, roomNID, tables.MembershipStateJoin, localOnly,
+			ctx, txn, roomNID, tables.MembershipStateJoin, localOnly,
 		)
 	}
 
-	return d.MembershipTable.SelectMembershipsFromRoom(ctx, roomNID, localOnly)
+	return d.MembershipTable.SelectMembershipsFromRoom(ctx, txn, roomNID, localOnly)
 }
 
 func (d *Database) GetInvitesForUser(
@@ -364,22 +431,28 @@ func (d *Database) GetInvitesForUser(
 	roomNID types.RoomNID,
 	targetUserNID types.EventStateKeyNID,
 ) (senderUserIDs []types.EventStateKeyNID, eventIDs []string, err error) {
-	return d.InvitesTable.SelectInviteActiveForUserInRoom(ctx, targetUserNID, roomNID)
+	return d.InvitesTable.SelectInviteActiveForUserInRoom(ctx, nil, targetUserNID, roomNID)
 }
 
 func (d *Database) Events(
 	ctx context.Context, eventNIDs []types.EventNID,
 ) ([]types.Event, error) {
-	eventJSONs, err := d.EventJSONTable.BulkSelectEventJSON(ctx, eventNIDs)
+	return d.events(ctx, nil, eventNIDs)
+}
+
+func (d *Database) events(
+	ctx context.Context, txn *sql.Tx, eventNIDs []types.EventNID,
+) ([]types.Event, error) {
+	eventJSONs, err := d.EventJSONTable.BulkSelectEventJSON(ctx, txn, eventNIDs)
 	if err != nil {
 		return nil, err
 	}
-	eventIDs, _ := d.EventsTable.BulkSelectEventID(ctx, eventNIDs)
+	eventIDs, _ := d.EventsTable.BulkSelectEventID(ctx, txn, eventNIDs)
 	if err != nil {
 		eventIDs = map[types.EventNID]string{}
 	}
 	var roomNIDs map[types.EventNID]types.RoomNID
-	roomNIDs, err = d.EventsTable.SelectRoomNIDsForEventNIDs(ctx, eventNIDs)
+	roomNIDs, err = d.EventsTable.SelectRoomNIDsForEventNIDs(ctx, txn, eventNIDs)
 	if err != nil {
 		return nil, err
 	}
@@ -398,7 +471,7 @@ func (d *Database) Events(
 		}
 		fetchNIDList = append(fetchNIDList, n)
 	}
-	dbRoomVersions, err := d.RoomsTable.SelectRoomVersionsForRoomNIDs(ctx, fetchNIDList)
+	dbRoomVersions, err := d.RoomsTable.SelectRoomVersionsForRoomNIDs(ctx, txn, fetchNIDList)
 	if err != nil {
 		return nil, err
 	}
@@ -440,19 +513,19 @@ func (d *Database) MembershipUpdater(
 	return updater, err
 }
 
-func (d *Database) GetLatestEventsForUpdate(
-	ctx context.Context, roomInfo types.RoomInfo,
-) (*LatestEventsUpdater, error) {
-	if d.GetLatestEventsForUpdateFn != nil {
-		return d.GetLatestEventsForUpdateFn(ctx, roomInfo)
+func (d *Database) GetRoomUpdater(
+	ctx context.Context, roomInfo *types.RoomInfo,
+) (*RoomUpdater, error) {
+	if d.GetRoomUpdaterFn != nil {
+		return d.GetRoomUpdaterFn(ctx, roomInfo)
 	}
 	txn, err := d.DB.Begin()
 	if err != nil {
 		return nil, err
 	}
-	var updater *LatestEventsUpdater
+	var updater *RoomUpdater
 	_ = d.Writer.Do(d.DB, txn, func(txn *sql.Tx) error {
-		updater, err = NewLatestEventsUpdater(ctx, d, txn, roomInfo)
+		updater, err = NewRoomUpdater(ctx, d, txn, roomInfo)
 		return err
 	})
 	return updater, err
@@ -461,6 +534,13 @@ func (d *Database) GetLatestEventsForUpdate(
 func (d *Database) StoreEvent(
 	ctx context.Context, event *gomatrixserverlib.Event,
 	authEventNIDs []types.EventNID, isRejected bool,
+) (types.EventNID, types.RoomNID, types.StateAtEvent, *gomatrixserverlib.Event, string, error) {
+	return d.storeEvent(ctx, nil, event, authEventNIDs, isRejected)
+}
+
+func (d *Database) storeEvent(
+	ctx context.Context, updater *RoomUpdater, event *gomatrixserverlib.Event,
+	authEventNIDs []types.EventNID, isRejected bool,
 ) (types.EventNID, types.RoomNID, types.StateAtEvent, *gomatrixserverlib.Event, string, error) {
 	var (
 		roomNID          types.RoomNID
@@ -472,8 +552,11 @@ func (d *Database) StoreEvent(
 		redactedEventID  string
 		err              error
 	)
-
-	err = d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
+	var txn *sql.Tx
+	if updater != nil {
+		txn = updater.txn
+	}
+	err = d.Writer.Do(d.DB, txn, func(txn *sql.Tx) error {
 		// TODO: Here we should aim to have two different code paths for new rooms
 		// vs existing ones.
 
@@ -546,42 +629,32 @@ func (d *Database) StoreEvent(
 	// events updater because it somewhat works as a mutex, ensuring
 	// that there's a row-level lock on the latest room events (well,
 	// on Postgres at least).
-	var roomInfo *types.RoomInfo
-	var updater *LatestEventsUpdater
 	if prevEvents := event.PrevEvents(); len(prevEvents) > 0 {
-		roomInfo, err = d.RoomInfo(ctx, event.RoomID())
-		if err != nil {
-			return 0, 0, types.StateAtEvent{}, nil, "", fmt.Errorf("d.RoomInfo: %w", err)
-		}
-		if roomInfo == nil && len(prevEvents) > 0 {
-			return 0, 0, types.StateAtEvent{}, nil, "", fmt.Errorf("expected room %q to exist", event.RoomID())
-		}
 		// Create an updater - NB: on sqlite this WILL create a txn as we are directly calling the shared DB form of
 		// GetLatestEventsForUpdate - not via the SQLiteDatabase form which has `nil` txns. This
 		// function only does SELECTs though so the created txn (at this point) is just a read txn like
 		// any other so this is fine. If we ever update GetLatestEventsForUpdate or NewLatestEventsUpdater
 		// to do writes however then this will need to go inside `Writer.Do`.
-		updater, err = d.GetLatestEventsForUpdate(ctx, *roomInfo)
-		if err != nil {
-			return 0, 0, types.StateAtEvent{}, nil, "", fmt.Errorf("NewLatestEventsUpdater: %w", err)
-		}
-		// Ensure that we atomically store prev events AND commit them. If we don't wrap StorePreviousEvents
-		// and EndTransaction in a writer then it's possible for a new write txn to be made between the two
-		// function calls which will then fail with 'database is locked'. This new write txn would HAVE to be
-		// something like SetRoomAlias/RemoveRoomAlias as normal input events are already done sequentially due to
-		// SupportsConcurrentRoomInputs() == false on sqlite, though this does not apply to setting room aliases
-		// as they don't go via InputRoomEvents
-		err = d.Writer.Do(d.DB, updater.txn, func(txn *sql.Tx) error {
-			if err = updater.StorePreviousEvents(eventNID, prevEvents); err != nil {
-				return fmt.Errorf("updater.StorePreviousEvents: %w", err)
+		succeeded := false
+		if updater == nil {
+			var roomInfo *types.RoomInfo
+			roomInfo, err = d.RoomInfo(ctx, event.RoomID())
+			if err != nil {
+				return 0, 0, types.StateAtEvent{}, nil, "", fmt.Errorf("d.RoomInfo: %w", err)
 			}
-			succeeded := true
-			err = sqlutil.EndTransaction(updater, &succeeded)
-			return err
-		})
-		if err != nil {
-			return 0, 0, types.StateAtEvent{}, nil, "", err
+			if roomInfo == nil && len(prevEvents) > 0 {
+				return 0, 0, types.StateAtEvent{}, nil, "", fmt.Errorf("expected room %q to exist", event.RoomID())
+			}
+			updater, err = d.GetRoomUpdater(ctx, roomInfo)
+			if err != nil {
+				return 0, 0, types.StateAtEvent{}, nil, "", fmt.Errorf("GetRoomUpdater: %w", err)
+			}
+			defer sqlutil.EndTransactionWithCheck(updater, &succeeded, &err)
 		}
+		if err = updater.StorePreviousEvents(eventNID, prevEvents); err != nil {
+			return 0, 0, types.StateAtEvent{}, nil, "", fmt.Errorf("updater.StorePreviousEvents: %w", err)
+		}
+		succeeded = true
 	}
 
 	return eventNID, roomNID, types.StateAtEvent{
@@ -603,7 +676,7 @@ func (d *Database) PublishRoom(ctx context.Context, roomID string, publish bool)
 }
 
 func (d *Database) GetPublishedRooms(ctx context.Context) ([]string, error) {
-	return d.PublishedTable.SelectAllPublishedRooms(ctx, true)
+	return d.PublishedTable.SelectAllPublishedRooms(ctx, nil, true)
 }
 
 func (d *Database) assignRoomNID(
@@ -875,14 +948,14 @@ func (d *Database) GetStateEvent(ctx context.Context, roomID, evType, stateKey s
 			eventNIDs = append(eventNIDs, e.EventNID)
 		}
 	}
-	eventIDs, _ := d.EventsTable.BulkSelectEventID(ctx, eventNIDs)
+	eventIDs, _ := d.EventsTable.BulkSelectEventID(ctx, nil, eventNIDs)
 	if err != nil {
 		eventIDs = map[types.EventNID]string{}
 	}
 	// return the event requested
 	for _, e := range entries {
 		if e.EventTypeNID == eventTypeNID && e.EventStateKeyNID == stateKeyNID {
-			data, err := d.EventJSONTable.BulkSelectEventJSON(ctx, []types.EventNID{e.EventNID})
+			data, err := d.EventJSONTable.BulkSelectEventJSON(ctx, nil, []types.EventNID{e.EventNID})
 			if err != nil {
 				return nil, err
 			}
@@ -922,11 +995,11 @@ func (d *Database) GetRoomsByMembership(ctx context.Context, userID, membership
 		}
 		return nil, fmt.Errorf("GetRoomsByMembership: cannot map user ID to state key NID: %w", err)
 	}
-	roomNIDs, err := d.MembershipTable.SelectRoomsWithMembership(ctx, stateKeyNID, membershipState)
+	roomNIDs, err := d.MembershipTable.SelectRoomsWithMembership(ctx, nil, stateKeyNID, membershipState)
 	if err != nil {
 		return nil, fmt.Errorf("GetRoomsByMembership: failed to SelectRoomsWithMembership: %w", err)
 	}
-	roomIDs, err := d.RoomsTable.BulkSelectRoomIDs(ctx, roomNIDs)
+	roomIDs, err := d.RoomsTable.BulkSelectRoomIDs(ctx, nil, roomNIDs)
 	if err != nil {
 		return nil, fmt.Errorf("GetRoomsByMembership: failed to lookup room nids: %w", err)
 	}
@@ -945,7 +1018,7 @@ func (d *Database) GetBulkStateContent(ctx context.Context, roomIDs []string, tu
 	}
 	// we don't bother failing the request if we get asked for event types we don't know about, as all that would result in is no matches which
 	// isn't a failure.
-	eventTypeNIDMap, err := d.EventTypesTable.BulkSelectEventTypeNID(ctx, eventTypes)
+	eventTypeNIDMap, err := d.EventTypesTable.BulkSelectEventTypeNID(ctx, nil, eventTypes)
 	if err != nil {
 		return nil, fmt.Errorf("GetBulkStateContent: failed to map event type nids: %w", err)
 	}
@@ -965,7 +1038,7 @@ func (d *Database) GetBulkStateContent(ctx context.Context, roomIDs []string, tu
 
 	}
 
-	eventStateKeyNIDMap, err := d.EventStateKeysTable.BulkSelectEventStateKeyNID(ctx, eventStateKeys)
+	eventStateKeyNIDMap, err := d.EventStateKeysTable.BulkSelectEventStateKeyNID(ctx, nil, eventStateKeys)
 	if err != nil {
 		return nil, fmt.Errorf("GetBulkStateContent: failed to map state key nids: %w", err)
 	}
@@ -999,11 +1072,11 @@ func (d *Database) GetBulkStateContent(ctx context.Context, roomIDs []string, tu
 			}
 		}
 	}
-	eventIDs, _ := d.EventsTable.BulkSelectEventID(ctx, eventNIDs)
+	eventIDs, _ := d.EventsTable.BulkSelectEventID(ctx, nil, eventNIDs)
 	if err != nil {
 		eventIDs = map[types.EventNID]string{}
 	}
-	events, err := d.EventJSONTable.BulkSelectEventJSON(ctx, eventNIDs)
+	events, err := d.EventJSONTable.BulkSelectEventJSON(ctx, nil, eventNIDs)
 	if err != nil {
 		return nil, fmt.Errorf("GetBulkStateContent: failed to load event JSON for event nids: %w", err)
 	}
@@ -1027,11 +1100,11 @@ func (d *Database) GetBulkStateContent(ctx context.Context, roomIDs []string, tu
 
 // JoinedUsersSetInRooms returns all joined users in the rooms given, along with the count of how many times they appear.
 func (d *Database) JoinedUsersSetInRooms(ctx context.Context, roomIDs []string) (map[string]int, error) {
-	roomNIDs, err := d.RoomsTable.BulkSelectRoomNIDs(ctx, roomIDs)
+	roomNIDs, err := d.RoomsTable.BulkSelectRoomNIDs(ctx, nil, roomIDs)
 	if err != nil {
 		return nil, err
 	}
-	userNIDToCount, err := d.MembershipTable.SelectJoinedUsersSetForRooms(ctx, roomNIDs)
+	userNIDToCount, err := d.MembershipTable.SelectJoinedUsersSetForRooms(ctx, nil, roomNIDs)
 	if err != nil {
 		return nil, err
 	}
@@ -1041,7 +1114,7 @@ func (d *Database) JoinedUsersSetInRooms(ctx context.Context, roomIDs []string)
 		stateKeyNIDs[i] = nid
 		i++
 	}
-	nidToUserID, err := d.EventStateKeysTable.BulkSelectEventStateKey(ctx, stateKeyNIDs)
+	nidToUserID, err := d.EventStateKeysTable.BulkSelectEventStateKey(ctx, nil, stateKeyNIDs)
 	if err != nil {
 		return nil, err
 	}
@@ -1057,12 +1130,12 @@ func (d *Database) JoinedUsersSetInRooms(ctx context.Context, roomIDs []string)
 
 // GetLocalServerInRoom returns true if we think we're in a given room or false otherwise.
 func (d *Database) GetLocalServerInRoom(ctx context.Context, roomNID types.RoomNID) (bool, error) {
-	return d.MembershipTable.SelectLocalServerInRoom(ctx, roomNID)
+	return d.MembershipTable.SelectLocalServerInRoom(ctx, nil, roomNID)
 }
 
 // GetServerInRoom returns true if we think a server is in a given room or false otherwise.
 func (d *Database) GetServerInRoom(ctx context.Context, roomNID types.RoomNID, serverName gomatrixserverlib.ServerName) (bool, error) {
-	return d.MembershipTable.SelectServerInRoom(ctx, roomNID, serverName)
+	return d.MembershipTable.SelectServerInRoom(ctx, nil, roomNID, serverName)
 }
 
 // GetKnownUsers searches all users that userID knows about.
@@ -1071,17 +1144,17 @@ func (d *Database) GetKnownUsers(ctx context.Context, userID, searchString strin
 	if err != nil {
 		return nil, err
 	}
-	return d.MembershipTable.SelectKnownUsers(ctx, stateKeyNID, searchString, limit)
+	return d.MembershipTable.SelectKnownUsers(ctx, nil, stateKeyNID, searchString, limit)
 }
 
 // GetKnownRooms returns a list of all rooms we know about.
 func (d *Database) GetKnownRooms(ctx context.Context) ([]string, error) {
-	return d.RoomsTable.SelectRoomIDs(ctx)
+	return d.RoomsTable.SelectRoomIDs(ctx, nil)
 }
 
 // ForgetRoom sets a users room to forgotten
 func (d *Database) ForgetRoom(ctx context.Context, userID, roomID string, forget bool) error {
-	roomNIDs, err := d.RoomsTable.BulkSelectRoomNIDs(ctx, []string{roomID})
+	roomNIDs, err := d.RoomsTable.BulkSelectRoomNIDs(ctx, nil, []string{roomID})
 	if err != nil {
 		return err
 	}
diff --git a/roomserver/storage/sqlite3/event_json_table.go b/roomserver/storage/sqlite3/event_json_table.go
index 53b219294..f470ea326 100644
--- a/roomserver/storage/sqlite3/event_json_table.go
+++ b/roomserver/storage/sqlite3/event_json_table.go
@@ -76,15 +76,20 @@ func (s *eventJSONStatements) InsertEventJSON(
 }
 
 func (s *eventJSONStatements) BulkSelectEventJSON(
-	ctx context.Context, eventNIDs []types.EventNID,
+	ctx context.Context, txn *sql.Tx, eventNIDs []types.EventNID,
 ) ([]tables.EventJSONPair, error) {
 	iEventNIDs := make([]interface{}, len(eventNIDs))
 	for k, v := range eventNIDs {
 		iEventNIDs[k] = v
 	}
 	selectOrig := strings.Replace(bulkSelectEventJSONSQL, "($1)", sqlutil.QueryVariadic(len(iEventNIDs)), 1)
-
-	rows, err := s.db.QueryContext(ctx, selectOrig, iEventNIDs...)
+	var rows *sql.Rows
+	var err error
+	if txn != nil {
+		rows, err = txn.QueryContext(ctx, selectOrig, iEventNIDs...)
+	} else {
+		rows, err = s.db.QueryContext(ctx, selectOrig, iEventNIDs...)
+	}
 	if err != nil {
 		return nil, err
 	}
diff --git a/roomserver/storage/sqlite3/event_state_keys_table.go b/roomserver/storage/sqlite3/event_state_keys_table.go
index 62fbce2d0..bf12d5b83 100644
--- a/roomserver/storage/sqlite3/event_state_keys_table.go
+++ b/roomserver/storage/sqlite3/event_state_keys_table.go
@@ -112,15 +112,20 @@ func (s *eventStateKeyStatements) SelectEventStateKeyNID(
 }
 
 func (s *eventStateKeyStatements) BulkSelectEventStateKeyNID(
-	ctx context.Context, eventStateKeys []string,
+	ctx context.Context, txn *sql.Tx, eventStateKeys []string,
 ) (map[string]types.EventStateKeyNID, error) {
 	iEventStateKeys := make([]interface{}, len(eventStateKeys))
 	for k, v := range eventStateKeys {
 		iEventStateKeys[k] = v
 	}
 	selectOrig := strings.Replace(bulkSelectEventStateKeySQL, "($1)", sqlutil.QueryVariadic(len(eventStateKeys)), 1)
-
-	rows, err := s.db.QueryContext(ctx, selectOrig, iEventStateKeys...)
+	var rows *sql.Rows
+	var err error
+	if txn != nil {
+		rows, err = txn.QueryContext(ctx, selectOrig, iEventStateKeys...)
+	} else {
+		rows, err = s.db.QueryContext(ctx, selectOrig, iEventStateKeys...)
+	}
 	if err != nil {
 		return nil, err
 	}
@@ -138,15 +143,19 @@ func (s *eventStateKeyStatements) BulkSelectEventStateKeyNID(
 }
 
 func (s *eventStateKeyStatements) BulkSelectEventStateKey(
-	ctx context.Context, eventStateKeyNIDs []types.EventStateKeyNID,
+	ctx context.Context, txn *sql.Tx, eventStateKeyNIDs []types.EventStateKeyNID,
 ) (map[types.EventStateKeyNID]string, error) {
 	iEventStateKeyNIDs := make([]interface{}, len(eventStateKeyNIDs))
 	for k, v := range eventStateKeyNIDs {
 		iEventStateKeyNIDs[k] = v
 	}
 	selectOrig := strings.Replace(bulkSelectEventStateKeyNIDSQL, "($1)", sqlutil.QueryVariadic(len(eventStateKeyNIDs)), 1)
-
-	rows, err := s.db.QueryContext(ctx, selectOrig, iEventStateKeyNIDs...)
+	selectPrep, err := s.db.Prepare(selectOrig)
+	if err != nil {
+		return nil, err
+	}
+	stmt := sqlutil.TxStmt(txn, selectPrep)
+	rows, err := stmt.QueryContext(ctx, iEventStateKeyNIDs...)
 	if err != nil {
 		return nil, err
 	}
diff --git a/roomserver/storage/sqlite3/event_types_table.go b/roomserver/storage/sqlite3/event_types_table.go
index 22df3fb22..f2c9c42fe 100644
--- a/roomserver/storage/sqlite3/event_types_table.go
+++ b/roomserver/storage/sqlite3/event_types_table.go
@@ -128,7 +128,7 @@ func (s *eventTypeStatements) SelectEventTypeNID(
 }
 
 func (s *eventTypeStatements) BulkSelectEventTypeNID(
-	ctx context.Context, eventTypes []string,
+	ctx context.Context, txn *sql.Tx, eventTypes []string,
 ) (map[string]types.EventTypeNID, error) {
 	///////////////
 	iEventTypes := make([]interface{}, len(eventTypes))
@@ -140,9 +140,10 @@ func (s *eventTypeStatements) BulkSelectEventTypeNID(
 	if err != nil {
 		return nil, err
 	}
+	stmt := sqlutil.TxStmt(txn, selectPrep)
 	///////////////
 
-	rows, err := selectPrep.QueryContext(ctx, iEventTypes...)
+	rows, err := stmt.QueryContext(ctx, iEventTypes...)
 	if err != nil {
 		return nil, err
 	}
diff --git a/roomserver/storage/sqlite3/events_table.go b/roomserver/storage/sqlite3/events_table.go
index 7483e2815..e1e6a597c 100644
--- a/roomserver/storage/sqlite3/events_table.go
+++ b/roomserver/storage/sqlite3/events_table.go
@@ -184,7 +184,7 @@ func (s *eventStatements) SelectEvent(
 // bulkSelectStateEventByID lookups a list of state events by event ID.
 // If any of the requested events are missing from the database it returns a types.MissingEventError
 func (s *eventStatements) BulkSelectStateEventByID(
-	ctx context.Context, eventIDs []string,
+	ctx context.Context, txn *sql.Tx, eventIDs []string,
 ) ([]types.StateEntry, error) {
 	///////////////
 	iEventIDs := make([]interface{}, len(eventIDs))
@@ -196,6 +196,7 @@ func (s *eventStatements) BulkSelectStateEventByID(
 	if err != nil {
 		return nil, err
 	}
+	selectStmt = sqlutil.TxStmt(txn, selectStmt)
 	///////////////
 
 	rows, err := selectStmt.QueryContext(ctx, iEventIDs...)
@@ -235,7 +236,7 @@ func (s *eventStatements) BulkSelectStateEventByID(
 // bulkSelectStateEventByID lookups a list of state events by event ID.
 // If any of the requested events are missing from the database it returns a types.MissingEventError
 func (s *eventStatements) BulkSelectStateEventByNID(
-	ctx context.Context, eventNIDs []types.EventNID,
+	ctx context.Context, txn *sql.Tx, eventNIDs []types.EventNID,
 	stateKeyTuples []types.StateKeyTuple,
 ) ([]types.StateEntry, error) {
 	tuples := stateKeyTupleSorter(stateKeyTuples)
@@ -263,6 +264,7 @@ func (s *eventStatements) BulkSelectStateEventByNID(
 	if err != nil {
 		return nil, fmt.Errorf("s.db.Prepare: %w", err)
 	}
+	selectStmt = sqlutil.TxStmt(txn, selectStmt)
 	rows, err := selectStmt.QueryContext(ctx, params...)
 	if err != nil {
 		return nil, fmt.Errorf("selectStmt.QueryContext: %w", err)
@@ -291,7 +293,7 @@ func (s *eventStatements) BulkSelectStateEventByNID(
 // If any of the requested events are missing from the database it returns a types.MissingEventError.
 // If we do not have the state for any of the requested events it returns a types.MissingEventError.
 func (s *eventStatements) BulkSelectStateAtEventByID(
-	ctx context.Context, eventIDs []string,
+	ctx context.Context, txn *sql.Tx, eventIDs []string,
 ) ([]types.StateAtEvent, error) {
 	///////////////
 	iEventIDs := make([]interface{}, len(eventIDs))
@@ -303,6 +305,7 @@ func (s *eventStatements) BulkSelectStateAtEventByID(
 	if err != nil {
 		return nil, err
 	}
+	selectStmt = sqlutil.TxStmt(txn, selectStmt)
 	///////////////
 	rows, err := selectStmt.QueryContext(ctx, iEventIDs...)
 	if err != nil {
@@ -381,6 +384,7 @@ func (s *eventStatements) BulkSelectStateAtEventAndReference(
 	if err != nil {
 		return nil, err
 	}
+	selectPrep = sqlutil.TxStmt(txn, selectPrep)
 	//////////////
 
 	rows, err := sqlutil.TxStmt(txn, selectPrep).QueryContext(ctx, iEventNIDs...)
@@ -454,7 +458,7 @@ func (s *eventStatements) BulkSelectEventReference(
 }
 
 // bulkSelectEventID returns a map from numeric event ID to string event ID.
-func (s *eventStatements) BulkSelectEventID(ctx context.Context, eventNIDs []types.EventNID) (map[types.EventNID]string, error) {
+func (s *eventStatements) BulkSelectEventID(ctx context.Context, txn *sql.Tx, eventNIDs []types.EventNID) (map[types.EventNID]string, error) {
 	///////////////
 	iEventNIDs := make([]interface{}, len(eventNIDs))
 	for k, v := range eventNIDs {
@@ -465,6 +469,7 @@ func (s *eventStatements) BulkSelectEventID(ctx context.Context, eventNIDs []typ
 	if err != nil {
 		return nil, err
 	}
+	selectStmt = sqlutil.TxStmt(txn, selectStmt)
 	///////////////
 
 	rows, err := selectStmt.QueryContext(ctx, iEventNIDs...)
@@ -490,7 +495,7 @@ func (s *eventStatements) BulkSelectEventID(ctx context.Context, eventNIDs []typ
 
 // bulkSelectEventNIDs returns a map from string event ID to numeric event ID.
 // If an event ID is not in the database then it is omitted from the map.
-func (s *eventStatements) BulkSelectEventNID(ctx context.Context, eventIDs []string) (map[string]types.EventNID, error) {
+func (s *eventStatements) BulkSelectEventNID(ctx context.Context, txn *sql.Tx, eventIDs []string) (map[string]types.EventNID, error) {
 	///////////////
 	iEventIDs := make([]interface{}, len(eventIDs))
 	for k, v := range eventIDs {
@@ -501,6 +506,7 @@ func (s *eventStatements) BulkSelectEventNID(ctx context.Context, eventIDs []str
 	if err != nil {
 		return nil, err
 	}
+	selectStmt = sqlutil.TxStmt(txn, selectStmt)
 	///////////////
 	rows, err := selectStmt.QueryContext(ctx, iEventIDs...)
 	if err != nil {
@@ -538,13 +544,14 @@ func (s *eventStatements) SelectMaxEventDepth(ctx context.Context, txn *sql.Tx,
 }
 
 func (s *eventStatements) SelectRoomNIDsForEventNIDs(
-	ctx context.Context, eventNIDs []types.EventNID,
+	ctx context.Context, txn *sql.Tx, eventNIDs []types.EventNID,
 ) (map[types.EventNID]types.RoomNID, error) {
 	sqlStr := strings.Replace(selectRoomNIDsForEventNIDsSQL, "($1)", sqlutil.QueryVariadic(len(eventNIDs)), 1)
 	sqlPrep, err := s.db.Prepare(sqlStr)
 	if err != nil {
 		return nil, err
 	}
+	sqlPrep = sqlutil.TxStmt(txn, sqlPrep)
 	iEventNIDs := make([]interface{}, len(eventNIDs))
 	for i, v := range eventNIDs {
 		iEventNIDs[i] = v
diff --git a/roomserver/storage/sqlite3/invite_table.go b/roomserver/storage/sqlite3/invite_table.go
index c1d7347ae..d54d313a9 100644
--- a/roomserver/storage/sqlite3/invite_table.go
+++ b/roomserver/storage/sqlite3/invite_table.go
@@ -88,8 +88,8 @@ func prepareInvitesTable(db *sql.DB) (tables.Invites, error) {
 }
 
 func (s *inviteStatements) InsertInviteEvent(
-	ctx context.Context,
-	txn *sql.Tx, inviteEventID string, roomNID types.RoomNID,
+	ctx context.Context, txn *sql.Tx,
+	inviteEventID string, roomNID types.RoomNID,
 	targetUserNID, senderUserNID types.EventStateKeyNID,
 	inviteEventJSON []byte,
 ) (bool, error) {
@@ -109,8 +109,8 @@ func (s *inviteStatements) InsertInviteEvent(
 }
 
 func (s *inviteStatements) UpdateInviteRetired(
-	ctx context.Context,
-	txn *sql.Tx, roomNID types.RoomNID, targetUserNID types.EventStateKeyNID,
+	ctx context.Context, txn *sql.Tx,
+	roomNID types.RoomNID, targetUserNID types.EventStateKeyNID,
 ) (eventIDs []string, err error) {
 	// gather all the event IDs we will retire
 	stmt := sqlutil.TxStmt(txn, s.selectInvitesAboutToRetireStmt)
@@ -134,10 +134,11 @@ func (s *inviteStatements) UpdateInviteRetired(
 
 // selectInviteActiveForUserInRoom returns a list of sender state key NIDs
 func (s *inviteStatements) SelectInviteActiveForUserInRoom(
-	ctx context.Context,
+	ctx context.Context, txn *sql.Tx,
 	targetUserNID types.EventStateKeyNID, roomNID types.RoomNID,
 ) ([]types.EventStateKeyNID, []string, error) {
-	rows, err := s.selectInviteActiveForUserInRoomStmt.QueryContext(
+	stmt := sqlutil.TxStmt(txn, s.selectInviteActiveForUserInRoomStmt)
+	rows, err := stmt.QueryContext(
 		ctx, targetUserNID, roomNID,
 	)
 	if err != nil {
diff --git a/roomserver/storage/sqlite3/membership_table.go b/roomserver/storage/sqlite3/membership_table.go
index 2e58431d3..181b4b4c9 100644
--- a/roomserver/storage/sqlite3/membership_table.go
+++ b/roomserver/storage/sqlite3/membership_table.go
@@ -184,17 +184,18 @@ func (s *membershipStatements) SelectMembershipForUpdate(
 }
 
 func (s *membershipStatements) SelectMembershipFromRoomAndTarget(
-	ctx context.Context,
+	ctx context.Context, txn *sql.Tx,
 	roomNID types.RoomNID, targetUserNID types.EventStateKeyNID,
 ) (eventNID types.EventNID, membership tables.MembershipState, forgotten bool, err error) {
-	err = s.selectMembershipFromRoomAndTargetStmt.QueryRowContext(
+	stmt := sqlutil.TxStmt(txn, s.selectMembershipFromRoomAndTargetStmt)
+	err = stmt.QueryRowContext(
 		ctx, roomNID, targetUserNID,
 	).Scan(&membership, &eventNID, &forgotten)
 	return
 }
 
 func (s *membershipStatements) SelectMembershipsFromRoom(
-	ctx context.Context,
+	ctx context.Context, txn *sql.Tx,
 	roomNID types.RoomNID, localOnly bool,
 ) (eventNIDs []types.EventNID, err error) {
 	var selectStmt *sql.Stmt
@@ -203,6 +204,7 @@ func (s *membershipStatements) SelectMembershipsFromRoom(
 	} else {
 		selectStmt = s.selectMembershipsFromRoomStmt
 	}
+	selectStmt = sqlutil.TxStmt(txn, selectStmt)
 	rows, err := selectStmt.QueryContext(ctx, roomNID)
 	if err != nil {
 		return nil, err
@@ -220,7 +222,7 @@ func (s *membershipStatements) SelectMembershipsFromRoom(
 }
 
 func (s *membershipStatements) SelectMembershipsFromRoomAndMembership(
-	ctx context.Context,
+	ctx context.Context, txn *sql.Tx,
 	roomNID types.RoomNID, membership tables.MembershipState, localOnly bool,
 ) (eventNIDs []types.EventNID, err error) {
 	var stmt *sql.Stmt
@@ -229,6 +231,7 @@ func (s *membershipStatements) SelectMembershipsFromRoomAndMembership(
 	} else {
 		stmt = s.selectMembershipsFromRoomAndMembershipStmt
 	}
+	stmt = sqlutil.TxStmt(txn, stmt)
 	rows, err := stmt.QueryContext(ctx, roomNID, membership)
 	if err != nil {
 		return
@@ -258,9 +261,10 @@ func (s *membershipStatements) UpdateMembership(
 }
 
 func (s *membershipStatements) SelectRoomsWithMembership(
-	ctx context.Context, userID types.EventStateKeyNID, membershipState tables.MembershipState,
+	ctx context.Context, txn *sql.Tx, userID types.EventStateKeyNID, membershipState tables.MembershipState,
 ) ([]types.RoomNID, error) {
-	rows, err := s.selectRoomsWithMembershipStmt.QueryContext(ctx, membershipState, userID)
+	stmt := sqlutil.TxStmt(txn, s.selectRoomsWithMembershipStmt)
+	rows, err := stmt.QueryContext(ctx, membershipState, userID)
 	if err != nil {
 		return nil, err
 	}
@@ -276,13 +280,19 @@ func (s *membershipStatements) SelectRoomsWithMembership(
 	return roomNIDs, nil
 }
 
-func (s *membershipStatements) SelectJoinedUsersSetForRooms(ctx context.Context, roomNIDs []types.RoomNID) (map[types.EventStateKeyNID]int, error) {
+func (s *membershipStatements) SelectJoinedUsersSetForRooms(ctx context.Context, txn *sql.Tx, roomNIDs []types.RoomNID) (map[types.EventStateKeyNID]int, error) {
 	iRoomNIDs := make([]interface{}, len(roomNIDs))
 	for i, v := range roomNIDs {
 		iRoomNIDs[i] = v
 	}
 	query := strings.Replace(selectJoinedUsersSetForRoomsSQL, "($1)", sqlutil.QueryVariadic(len(iRoomNIDs)), 1)
-	rows, err := s.db.QueryContext(ctx, query, iRoomNIDs...)
+	var rows *sql.Rows
+	var err error
+	if txn != nil {
+		rows, err = txn.QueryContext(ctx, query, iRoomNIDs...)
+	} else {
+		rows, err = s.db.QueryContext(ctx, query, iRoomNIDs...)
+	}
 	if err != nil {
 		return nil, err
 	}
@@ -299,8 +309,9 @@ func (s *membershipStatements) SelectJoinedUsersSetForRooms(ctx context.Context,
 	return result, rows.Err()
 }
 
-func (s *membershipStatements) SelectKnownUsers(ctx context.Context, userID types.EventStateKeyNID, searchString string, limit int) ([]string, error) {
-	rows, err := s.selectKnownUsersStmt.QueryContext(ctx, userID, fmt.Sprintf("%%%s%%", searchString), limit)
+func (s *membershipStatements) SelectKnownUsers(ctx context.Context, txn *sql.Tx, userID types.EventStateKeyNID, searchString string, limit int) ([]string, error) {
+	stmt := sqlutil.TxStmt(txn, s.selectKnownUsersStmt)
+	rows, err := stmt.QueryContext(ctx, userID, fmt.Sprintf("%%%s%%", searchString), limit)
 	if err != nil {
 		return nil, err
 	}
@@ -317,8 +328,8 @@ func (s *membershipStatements) SelectKnownUsers(ctx context.Context, userID type
 }
 
 func (s *membershipStatements) UpdateForgetMembership(
-	ctx context.Context,
-	txn *sql.Tx, roomNID types.RoomNID, targetUserNID types.EventStateKeyNID,
+	ctx context.Context, txn *sql.Tx,
+	roomNID types.RoomNID, targetUserNID types.EventStateKeyNID,
 	forget bool,
 ) error {
 	_, err := sqlutil.TxStmt(txn, s.updateMembershipForgetRoomStmt).ExecContext(
@@ -327,9 +338,10 @@ func (s *membershipStatements) UpdateForgetMembership(
 	return err
 }
 
-func (s *membershipStatements) SelectLocalServerInRoom(ctx context.Context, roomNID types.RoomNID) (bool, error) {
+func (s *membershipStatements) SelectLocalServerInRoom(ctx context.Context, txn *sql.Tx, roomNID types.RoomNID) (bool, error) {
 	var nid types.RoomNID
-	err := s.selectLocalServerInRoomStmt.QueryRowContext(ctx, tables.MembershipStateJoin, roomNID).Scan(&nid)
+	stmt := sqlutil.TxStmt(txn, s.selectLocalServerInRoomStmt)
+	err := stmt.QueryRowContext(ctx, tables.MembershipStateJoin, roomNID).Scan(&nid)
 	if err != nil {
 		if err == sql.ErrNoRows {
 			return false, nil
@@ -340,9 +352,10 @@ func (s *membershipStatements) SelectLocalServerInRoom(ctx context.Context, room
 	return found, nil
 }
 
-func (s *membershipStatements) SelectServerInRoom(ctx context.Context, roomNID types.RoomNID, serverName gomatrixserverlib.ServerName) (bool, error) {
+func (s *membershipStatements) SelectServerInRoom(ctx context.Context, txn *sql.Tx, roomNID types.RoomNID, serverName gomatrixserverlib.ServerName) (bool, error) {
 	var nid types.RoomNID
-	err := s.selectServerInRoomStmt.QueryRowContext(ctx, tables.MembershipStateJoin, roomNID, serverName).Scan(&nid)
+	stmt := sqlutil.TxStmt(txn, s.selectServerInRoomStmt)
+	err := stmt.QueryRowContext(ctx, tables.MembershipStateJoin, roomNID, serverName).Scan(&nid)
 	if err != nil {
 		if err == sql.ErrNoRows {
 			return false, nil
diff --git a/roomserver/storage/sqlite3/published_table.go b/roomserver/storage/sqlite3/published_table.go
index b07c0ac42..9e416ace3 100644
--- a/roomserver/storage/sqlite3/published_table.go
+++ b/roomserver/storage/sqlite3/published_table.go
@@ -75,9 +75,10 @@ func (s *publishedStatements) UpsertRoomPublished(
 }
 
 func (s *publishedStatements) SelectPublishedFromRoomID(
-	ctx context.Context, roomID string,
+	ctx context.Context, txn *sql.Tx, roomID string,
 ) (published bool, err error) {
-	err = s.selectPublishedStmt.QueryRowContext(ctx, roomID).Scan(&published)
+	stmt := sqlutil.TxStmt(txn, s.selectPublishedStmt)
+	err = stmt.QueryRowContext(ctx, roomID).Scan(&published)
 	if err == sql.ErrNoRows {
 		return false, nil
 	}
@@ -85,9 +86,10 @@ func (s *publishedStatements) SelectPublishedFromRoomID(
 }
 
 func (s *publishedStatements) SelectAllPublishedRooms(
-	ctx context.Context, published bool,
+	ctx context.Context, txn *sql.Tx, published bool,
 ) ([]string, error) {
-	rows, err := s.selectAllPublishedStmt.QueryContext(ctx, published)
+	stmt := sqlutil.TxStmt(txn, s.selectAllPublishedStmt)
+	rows, err := stmt.QueryContext(ctx, published)
 	if err != nil {
 		return nil, err
 	}
diff --git a/roomserver/storage/sqlite3/room_aliases_table.go b/roomserver/storage/sqlite3/room_aliases_table.go
index 323945b88..7c7bead95 100644
--- a/roomserver/storage/sqlite3/room_aliases_table.go
+++ b/roomserver/storage/sqlite3/room_aliases_table.go
@@ -91,9 +91,10 @@ func (s *roomAliasesStatements) InsertRoomAlias(
 }
 
 func (s *roomAliasesStatements) SelectRoomIDFromAlias(
-	ctx context.Context, alias string,
+	ctx context.Context, txn *sql.Tx, alias string,
 ) (roomID string, err error) {
-	err = s.selectRoomIDFromAliasStmt.QueryRowContext(ctx, alias).Scan(&roomID)
+	stmt := sqlutil.TxStmt(txn, s.selectRoomIDFromAliasStmt)
+	err = stmt.QueryRowContext(ctx, alias).Scan(&roomID)
 	if err == sql.ErrNoRows {
 		return "", nil
 	}
@@ -101,10 +102,11 @@ func (s *roomAliasesStatements) SelectRoomIDFromAlias(
 }
 
 func (s *roomAliasesStatements) SelectAliasesFromRoomID(
-	ctx context.Context, roomID string,
+	ctx context.Context, txn *sql.Tx, roomID string,
 ) (aliases []string, err error) {
 	aliases = []string{}
-	rows, err := s.selectAliasesFromRoomIDStmt.QueryContext(ctx, roomID)
+	stmt := sqlutil.TxStmt(txn, s.selectAliasesFromRoomIDStmt)
+	rows, err := stmt.QueryContext(ctx, roomID)
 	if err != nil {
 		return
 	}
@@ -124,9 +126,10 @@ func (s *roomAliasesStatements) SelectAliasesFromRoomID(
 }
 
 func (s *roomAliasesStatements) SelectCreatorIDFromAlias(
-	ctx context.Context, alias string,
+	ctx context.Context, txn *sql.Tx, alias string,
 ) (creatorID string, err error) {
-	err = s.selectCreatorIDFromAliasStmt.QueryRowContext(ctx, alias).Scan(&creatorID)
+	stmt := sqlutil.TxStmt(txn, s.selectCreatorIDFromAliasStmt)
+	err = stmt.QueryRowContext(ctx, alias).Scan(&creatorID)
 	if err == sql.ErrNoRows {
 		return "", nil
 	}
diff --git a/roomserver/storage/sqlite3/rooms_table.go b/roomserver/storage/sqlite3/rooms_table.go
index c441daec0..5413475e2 100644
--- a/roomserver/storage/sqlite3/rooms_table.go
+++ b/roomserver/storage/sqlite3/rooms_table.go
@@ -107,8 +107,9 @@ func prepareRoomsTable(db *sql.DB) (tables.Rooms, error) {
 	}.Prepare(db)
 }
 
-func (s *roomStatements) SelectRoomIDs(ctx context.Context) ([]string, error) {
-	rows, err := s.selectRoomIDsStmt.QueryContext(ctx)
+func (s *roomStatements) SelectRoomIDs(ctx context.Context, txn *sql.Tx) ([]string, error) {
+	stmt := sqlutil.TxStmt(txn, s.selectRoomIDsStmt)
+	rows, err := stmt.QueryContext(ctx)
 	if err != nil {
 		return nil, err
 	}
@@ -124,10 +125,11 @@ func (s *roomStatements) SelectRoomIDs(ctx context.Context) ([]string, error) {
 	return roomIDs, nil
 }
 
-func (s *roomStatements) SelectRoomInfo(ctx context.Context, roomID string) (*types.RoomInfo, error) {
+func (s *roomStatements) SelectRoomInfo(ctx context.Context, txn *sql.Tx, roomID string) (*types.RoomInfo, error) {
 	var info types.RoomInfo
 	var latestNIDsJSON string
-	err := s.selectRoomInfoStmt.QueryRowContext(ctx, roomID).Scan(
+	stmt := sqlutil.TxStmt(txn, s.selectRoomInfoStmt)
+	err := stmt.QueryRowContext(ctx, roomID).Scan(
 		&info.RoomVersion, &info.RoomNID, &info.StateSnapshotNID, &latestNIDsJSON,
 	)
 	if err != nil {
@@ -224,13 +226,14 @@ func (s *roomStatements) UpdateLatestEventNIDs(
 }
 
 func (s *roomStatements) SelectRoomVersionsForRoomNIDs(
-	ctx context.Context, roomNIDs []types.RoomNID,
+	ctx context.Context, txn *sql.Tx, roomNIDs []types.RoomNID,
 ) (map[types.RoomNID]gomatrixserverlib.RoomVersion, error) {
 	sqlStr := strings.Replace(selectRoomVersionsForRoomNIDsSQL, "($1)", sqlutil.QueryVariadic(len(roomNIDs)), 1)
 	sqlPrep, err := s.db.Prepare(sqlStr)
 	if err != nil {
 		return nil, err
 	}
+	sqlPrep = sqlutil.TxStmt(txn, sqlPrep)
 	iRoomNIDs := make([]interface{}, len(roomNIDs))
 	for i, v := range roomNIDs {
 		iRoomNIDs[i] = v
@@ -252,13 +255,19 @@ func (s *roomStatements) SelectRoomVersionsForRoomNIDs(
 	return result, nil
 }
 
-func (s *roomStatements) BulkSelectRoomIDs(ctx context.Context, roomNIDs []types.RoomNID) ([]string, error) {
+func (s *roomStatements) BulkSelectRoomIDs(ctx context.Context, txn *sql.Tx, roomNIDs []types.RoomNID) ([]string, error) {
 	iRoomNIDs := make([]interface{}, len(roomNIDs))
 	for i, v := range roomNIDs {
 		iRoomNIDs[i] = v
 	}
 	sqlQuery := strings.Replace(bulkSelectRoomIDsSQL, "($1)", sqlutil.QueryVariadic(len(roomNIDs)), 1)
-	rows, err := s.db.QueryContext(ctx, sqlQuery, iRoomNIDs...)
+	var rows *sql.Rows
+	var err error
+	if txn != nil {
+		rows, err = txn.QueryContext(ctx, sqlQuery, iRoomNIDs...)
+	} else {
+		rows, err = s.db.QueryContext(ctx, sqlQuery, iRoomNIDs...)
+	}
 	if err != nil {
 		return nil, err
 	}
@@ -274,13 +283,19 @@ func (s *roomStatements) BulkSelectRoomIDs(ctx context.Context, roomNIDs []types
 	return roomIDs, nil
 }
 
-func (s *roomStatements) BulkSelectRoomNIDs(ctx context.Context, roomIDs []string) ([]types.RoomNID, error) {
+func (s *roomStatements) BulkSelectRoomNIDs(ctx context.Context, txn *sql.Tx, roomIDs []string) ([]types.RoomNID, error) {
 	iRoomIDs := make([]interface{}, len(roomIDs))
 	for i, v := range roomIDs {
 		iRoomIDs[i] = v
 	}
 	sqlQuery := strings.Replace(bulkSelectRoomNIDsSQL, "($1)", sqlutil.QueryVariadic(len(roomIDs)), 1)
-	rows, err := s.db.QueryContext(ctx, sqlQuery, iRoomIDs...)
+	var rows *sql.Rows
+	var err error
+	if txn != nil {
+		rows, err = txn.QueryContext(ctx, sqlQuery, iRoomIDs...)
+	} else {
+		rows, err = s.db.QueryContext(ctx, sqlQuery, iRoomIDs...)
+	}
 	if err != nil {
 		return nil, err
 	}
diff --git a/roomserver/storage/sqlite3/state_block_table.go b/roomserver/storage/sqlite3/state_block_table.go
index 58b0b5dc2..d51fc492d 100644
--- a/roomserver/storage/sqlite3/state_block_table.go
+++ b/roomserver/storage/sqlite3/state_block_table.go
@@ -81,8 +81,7 @@ func prepareStateBlockTable(db *sql.DB) (tables.StateBlock, error) {
 }
 
 func (s *stateBlockStatements) BulkInsertStateData(
-	ctx context.Context,
-	txn *sql.Tx,
+	ctx context.Context, txn *sql.Tx,
 	entries types.StateEntries,
 ) (id types.StateBlockNID, err error) {
 	entries = entries[:util.SortAndUnique(entries)]
@@ -94,14 +93,15 @@ func (s *stateBlockStatements) BulkInsertStateData(
 	if err != nil {
 		return 0, fmt.Errorf("json.Marshal: %w", err)
 	}
-	err = s.insertStateDataStmt.QueryRowContext(
+	stmt := sqlutil.TxStmt(txn, s.insertStateDataStmt)
+	err = stmt.QueryRowContext(
 		ctx, nids.Hash(), js,
 	).Scan(&id)
 	return
 }
 
 func (s *stateBlockStatements) BulkSelectStateBlockEntries(
-	ctx context.Context, stateBlockNIDs types.StateBlockNIDs,
+	ctx context.Context, txn *sql.Tx, stateBlockNIDs types.StateBlockNIDs,
 ) ([][]types.EventNID, error) {
 	intfs := make([]interface{}, len(stateBlockNIDs))
 	for i := range stateBlockNIDs {
@@ -112,6 +112,7 @@ func (s *stateBlockStatements) BulkSelectStateBlockEntries(
 	if err != nil {
 		return nil, err
 	}
+	selectStmt = sqlutil.TxStmt(txn, selectStmt)
 	rows, err := selectStmt.QueryContext(ctx, intfs...)
 	if err != nil {
 		return nil, err
diff --git a/roomserver/storage/sqlite3/state_snapshot_table.go b/roomserver/storage/sqlite3/state_snapshot_table.go
index 040d99ae6..3c4bde3f5 100644
--- a/roomserver/storage/sqlite3/state_snapshot_table.go
+++ b/roomserver/storage/sqlite3/state_snapshot_table.go
@@ -106,7 +106,7 @@ func (s *stateSnapshotStatements) InsertState(
 }
 
 func (s *stateSnapshotStatements) BulkSelectStateBlockNIDs(
-	ctx context.Context, stateNIDs []types.StateSnapshotNID,
+	ctx context.Context, txn *sql.Tx, stateNIDs []types.StateSnapshotNID,
 ) ([]types.StateBlockNIDList, error) {
 	nids := make([]interface{}, len(stateNIDs))
 	for k, v := range stateNIDs {
@@ -117,6 +117,7 @@ func (s *stateSnapshotStatements) BulkSelectStateBlockNIDs(
 	if err != nil {
 		return nil, err
 	}
+	selectStmt = sqlutil.TxStmt(txn, selectStmt)
 
 	rows, err := selectStmt.QueryContext(ctx, nids...)
 	if err != nil {
diff --git a/roomserver/storage/sqlite3/storage.go b/roomserver/storage/sqlite3/storage.go
index 1fcc7989d..325c253b5 100644
--- a/roomserver/storage/sqlite3/storage.go
+++ b/roomserver/storage/sqlite3/storage.go
@@ -172,23 +172,23 @@ func (d *Database) prepare(db *sql.DB, cache caching.RoomServerCaches) error {
 		return err
 	}
 	d.Database = shared.Database{
-		DB:                         db,
-		Cache:                      cache,
-		Writer:                     sqlutil.NewExclusiveWriter(),
-		EventsTable:                events,
-		EventTypesTable:            eventTypes,
-		EventStateKeysTable:        eventStateKeys,
-		EventJSONTable:             eventJSON,
-		RoomsTable:                 rooms,
-		StateBlockTable:            stateBlock,
-		StateSnapshotTable:         stateSnapshot,
-		PrevEventsTable:            prevEvents,
-		RoomAliasesTable:           roomAliases,
-		InvitesTable:               invites,
-		MembershipTable:            membership,
-		PublishedTable:             published,
-		RedactionsTable:            redactions,
-		GetLatestEventsForUpdateFn: d.GetLatestEventsForUpdate,
+		DB:                  db,
+		Cache:               cache,
+		Writer:              sqlutil.NewExclusiveWriter(),
+		EventsTable:         events,
+		EventTypesTable:     eventTypes,
+		EventStateKeysTable: eventStateKeys,
+		EventJSONTable:      eventJSON,
+		RoomsTable:          rooms,
+		StateBlockTable:     stateBlock,
+		StateSnapshotTable:  stateSnapshot,
+		PrevEventsTable:     prevEvents,
+		RoomAliasesTable:    roomAliases,
+		InvitesTable:        invites,
+		MembershipTable:     membership,
+		PublishedTable:      published,
+		RedactionsTable:     redactions,
+		GetRoomUpdaterFn:    d.GetRoomUpdater,
 	}
 	return nil
 }
@@ -201,16 +201,16 @@ func (d *Database) SupportsConcurrentRoomInputs() bool {
 	return false
 }
 
-func (d *Database) GetLatestEventsForUpdate(
-	ctx context.Context, roomInfo types.RoomInfo,
-) (*shared.LatestEventsUpdater, error) {
+func (d *Database) GetRoomUpdater(
+	ctx context.Context, roomInfo *types.RoomInfo,
+) (*shared.RoomUpdater, error) {
 	// TODO: Do not use transactions. We should be holding open this transaction but we cannot have
 	// multiple write transactions on sqlite. The code will perform additional
 	// write transactions independent of this one which will consistently cause
 	// 'database is locked' errors. As sqlite doesn't support multi-process on the
 	// same DB anyway, and we only execute updates sequentially, the only worries
 	// are for rolling back when things go wrong. (atomicity)
-	return shared.NewLatestEventsUpdater(ctx, &d.Database, nil, roomInfo)
+	return shared.NewRoomUpdater(ctx, &d.Database, nil, roomInfo)
 }
 
 func (d *Database) MembershipUpdater(
diff --git a/roomserver/storage/tables/interface.go b/roomserver/storage/tables/interface.go
index 6ad7ed2e8..fed39b944 100644
--- a/roomserver/storage/tables/interface.go
+++ b/roomserver/storage/tables/interface.go
@@ -18,20 +18,20 @@ type EventJSONPair struct {
 type EventJSON interface {
 	// Insert the event JSON. On conflict, replace the event JSON with the new value (for redactions).
 	InsertEventJSON(ctx context.Context, tx *sql.Tx, eventNID types.EventNID, eventJSON []byte) error
-	BulkSelectEventJSON(ctx context.Context, eventNIDs []types.EventNID) ([]EventJSONPair, error)
+	BulkSelectEventJSON(ctx context.Context, tx *sql.Tx, eventNIDs []types.EventNID) ([]EventJSONPair, error)
 }
 
 type EventTypes interface {
 	InsertEventTypeNID(ctx context.Context, tx *sql.Tx, eventType string) (types.EventTypeNID, error)
 	SelectEventTypeNID(ctx context.Context, tx *sql.Tx, eventType string) (types.EventTypeNID, error)
-	BulkSelectEventTypeNID(ctx context.Context, eventTypes []string) (map[string]types.EventTypeNID, error)
+	BulkSelectEventTypeNID(ctx context.Context, txn *sql.Tx, eventTypes []string) (map[string]types.EventTypeNID, error)
 }
 
 type EventStateKeys interface {
 	InsertEventStateKeyNID(ctx context.Context, txn *sql.Tx, eventStateKey string) (types.EventStateKeyNID, error)
 	SelectEventStateKeyNID(ctx context.Context, txn *sql.Tx, eventStateKey string) (types.EventStateKeyNID, error)
-	BulkSelectEventStateKeyNID(ctx context.Context, eventStateKeys []string) (map[string]types.EventStateKeyNID, error)
-	BulkSelectEventStateKey(ctx context.Context, eventStateKeyNIDs []types.EventStateKeyNID) (map[types.EventStateKeyNID]string, error)
+	BulkSelectEventStateKeyNID(ctx context.Context, txn *sql.Tx, eventStateKeys []string) (map[string]types.EventStateKeyNID, error)
+	BulkSelectEventStateKey(ctx context.Context, txn *sql.Tx, eventStateKeyNIDs []types.EventStateKeyNID) (map[types.EventStateKeyNID]string, error)
 }
 
 type Events interface {
@@ -42,12 +42,12 @@ type Events interface {
 	SelectEvent(ctx context.Context, txn *sql.Tx, eventID string) (types.EventNID, types.StateSnapshotNID, error)
 	// bulkSelectStateEventByID lookups a list of state events by event ID.
 	// If any of the requested events are missing from the database it returns a types.MissingEventError
-	BulkSelectStateEventByID(ctx context.Context, eventIDs []string) ([]types.StateEntry, error)
-	BulkSelectStateEventByNID(ctx context.Context, eventNIDs []types.EventNID, stateKeyTuples []types.StateKeyTuple) ([]types.StateEntry, error)
+	BulkSelectStateEventByID(ctx context.Context, txn *sql.Tx, eventIDs []string) ([]types.StateEntry, error)
+	BulkSelectStateEventByNID(ctx context.Context, txn *sql.Tx, eventNIDs []types.EventNID, stateKeyTuples []types.StateKeyTuple) ([]types.StateEntry, error)
 	// BulkSelectStateAtEventByID lookups the state at a list of events by event ID.
 	// If any of the requested events are missing from the database it returns a types.MissingEventError.
 	// If we do not have the state for any of the requested events it returns a types.MissingEventError.
-	BulkSelectStateAtEventByID(ctx context.Context, eventIDs []string) ([]types.StateAtEvent, error)
+	BulkSelectStateAtEventByID(ctx context.Context, txn *sql.Tx, eventIDs []string) ([]types.StateAtEvent, error)
 	UpdateEventState(ctx context.Context, txn *sql.Tx, eventNID types.EventNID, stateNID types.StateSnapshotNID) error
 	SelectEventSentToOutput(ctx context.Context, txn *sql.Tx, eventNID types.EventNID) (sentToOutput bool, err error)
 	UpdateEventSentToOutput(ctx context.Context, txn *sql.Tx, eventNID types.EventNID) error
@@ -55,12 +55,12 @@ type Events interface {
 	BulkSelectStateAtEventAndReference(ctx context.Context, txn *sql.Tx, eventNIDs []types.EventNID) ([]types.StateAtEventAndReference, error)
 	BulkSelectEventReference(ctx context.Context, txn *sql.Tx, eventNIDs []types.EventNID) ([]gomatrixserverlib.EventReference, error)
 	// BulkSelectEventID returns a map from numeric event ID to string event ID.
-	BulkSelectEventID(ctx context.Context, eventNIDs []types.EventNID) (map[types.EventNID]string, error)
+	BulkSelectEventID(ctx context.Context, txn *sql.Tx, eventNIDs []types.EventNID) (map[types.EventNID]string, error)
 	// BulkSelectEventNIDs returns a map from string event ID to numeric event ID.
 	// If an event ID is not in the database then it is omitted from the map.
-	BulkSelectEventNID(ctx context.Context, eventIDs []string) (map[string]types.EventNID, error)
+	BulkSelectEventNID(ctx context.Context, txn *sql.Tx, eventIDs []string) (map[string]types.EventNID, error)
 	SelectMaxEventDepth(ctx context.Context, txn *sql.Tx, eventNIDs []types.EventNID) (int64, error)
-	SelectRoomNIDsForEventNIDs(ctx context.Context, eventNIDs []types.EventNID) (roomNIDs map[types.EventNID]types.RoomNID, err error)
+	SelectRoomNIDsForEventNIDs(ctx context.Context, txn *sql.Tx, eventNIDs []types.EventNID) (roomNIDs map[types.EventNID]types.RoomNID, err error)
 }
 
 type Rooms interface {
@@ -69,29 +69,29 @@ type Rooms interface {
 	SelectLatestEventNIDs(ctx context.Context, txn *sql.Tx, roomNID types.RoomNID) ([]types.EventNID, types.StateSnapshotNID, error)
 	SelectLatestEventsNIDsForUpdate(ctx context.Context, txn *sql.Tx, roomNID types.RoomNID) ([]types.EventNID, types.EventNID, types.StateSnapshotNID, error)
 	UpdateLatestEventNIDs(ctx context.Context, txn *sql.Tx, roomNID types.RoomNID, eventNIDs []types.EventNID, lastEventSentNID types.EventNID, stateSnapshotNID types.StateSnapshotNID) error
-	SelectRoomVersionsForRoomNIDs(ctx context.Context, roomNID []types.RoomNID) (map[types.RoomNID]gomatrixserverlib.RoomVersion, error)
-	SelectRoomInfo(ctx context.Context, roomID string) (*types.RoomInfo, error)
-	SelectRoomIDs(ctx context.Context) ([]string, error)
-	BulkSelectRoomIDs(ctx context.Context, roomNIDs []types.RoomNID) ([]string, error)
-	BulkSelectRoomNIDs(ctx context.Context, roomIDs []string) ([]types.RoomNID, error)
+	SelectRoomVersionsForRoomNIDs(ctx context.Context, txn *sql.Tx, roomNID []types.RoomNID) (map[types.RoomNID]gomatrixserverlib.RoomVersion, error)
+	SelectRoomInfo(ctx context.Context, txn *sql.Tx, roomID string) (*types.RoomInfo, error)
+	SelectRoomIDs(ctx context.Context, txn *sql.Tx) ([]string, error)
+	BulkSelectRoomIDs(ctx context.Context, txn *sql.Tx, roomNIDs []types.RoomNID) ([]string, error)
+	BulkSelectRoomNIDs(ctx context.Context, txn *sql.Tx, roomIDs []string) ([]types.RoomNID, error)
 }
 
 type StateSnapshot interface {
 	InsertState(ctx context.Context, txn *sql.Tx, roomNID types.RoomNID, stateBlockNIDs types.StateBlockNIDs) (stateNID types.StateSnapshotNID, err error)
-	BulkSelectStateBlockNIDs(ctx context.Context, stateNIDs []types.StateSnapshotNID) ([]types.StateBlockNIDList, error)
+	BulkSelectStateBlockNIDs(ctx context.Context, txn *sql.Tx, stateNIDs []types.StateSnapshotNID) ([]types.StateBlockNIDList, error)
 }
 
 type StateBlock interface {
 	BulkInsertStateData(ctx context.Context, txn *sql.Tx, entries types.StateEntries) (types.StateBlockNID, error)
-	BulkSelectStateBlockEntries(ctx context.Context, stateBlockNIDs types.StateBlockNIDs) ([][]types.EventNID, error)
+	BulkSelectStateBlockEntries(ctx context.Context, txn *sql.Tx, stateBlockNIDs types.StateBlockNIDs) ([][]types.EventNID, error)
 	//BulkSelectFilteredStateBlockEntries(ctx context.Context, stateBlockNIDs []types.StateBlockNID, stateKeyTuples []types.StateKeyTuple) ([]types.StateEntryList, error)
 }
 
 type RoomAliases interface {
 	InsertRoomAlias(ctx context.Context, txn *sql.Tx, alias string, roomID string, creatorUserID string) (err error)
-	SelectRoomIDFromAlias(ctx context.Context, alias string) (roomID string, err error)
-	SelectAliasesFromRoomID(ctx context.Context, roomID string) ([]string, error)
-	SelectCreatorIDFromAlias(ctx context.Context, alias string) (creatorID string, err error)
+	SelectRoomIDFromAlias(ctx context.Context, txn *sql.Tx, alias string) (roomID string, err error)
+	SelectAliasesFromRoomID(ctx context.Context, txn *sql.Tx, roomID string) ([]string, error)
+	SelectCreatorIDFromAlias(ctx context.Context, txn *sql.Tx, alias string) (creatorID string, err error)
 	DeleteRoomAlias(ctx context.Context, txn *sql.Tx, alias string) (err error)
 }
 
@@ -106,7 +106,7 @@ type Invites interface {
 	InsertInviteEvent(ctx context.Context, txn *sql.Tx, inviteEventID string, roomNID types.RoomNID, targetUserNID, senderUserNID types.EventStateKeyNID, inviteEventJSON []byte) (bool, error)
 	UpdateInviteRetired(ctx context.Context, txn *sql.Tx, roomNID types.RoomNID, targetUserNID types.EventStateKeyNID) ([]string, error)
 	// SelectInviteActiveForUserInRoom returns a list of sender state key NIDs and invite event IDs matching those nids.
-	SelectInviteActiveForUserInRoom(ctx context.Context, targetUserNID types.EventStateKeyNID, roomNID types.RoomNID) ([]types.EventStateKeyNID, []string, error)
+	SelectInviteActiveForUserInRoom(ctx context.Context, txn *sql.Tx, targetUserNID types.EventStateKeyNID, roomNID types.RoomNID) ([]types.EventStateKeyNID, []string, error)
 }
 
 type MembershipState int64
@@ -121,24 +121,24 @@ const (
 type Membership interface {
 	InsertMembership(ctx context.Context, txn *sql.Tx, roomNID types.RoomNID, targetUserNID types.EventStateKeyNID, localTarget bool) error
 	SelectMembershipForUpdate(ctx context.Context, txn *sql.Tx, roomNID types.RoomNID, targetUserNID types.EventStateKeyNID) (MembershipState, error)
-	SelectMembershipFromRoomAndTarget(ctx context.Context, roomNID types.RoomNID, targetUserNID types.EventStateKeyNID) (types.EventNID, MembershipState, bool, error)
-	SelectMembershipsFromRoom(ctx context.Context, roomNID types.RoomNID, localOnly bool) (eventNIDs []types.EventNID, err error)
-	SelectMembershipsFromRoomAndMembership(ctx context.Context, roomNID types.RoomNID, membership MembershipState, localOnly bool) (eventNIDs []types.EventNID, err error)
+	SelectMembershipFromRoomAndTarget(ctx context.Context, txn *sql.Tx, roomNID types.RoomNID, targetUserNID types.EventStateKeyNID) (types.EventNID, MembershipState, bool, error)
+	SelectMembershipsFromRoom(ctx context.Context, txn *sql.Tx, roomNID types.RoomNID, localOnly bool) (eventNIDs []types.EventNID, err error)
+	SelectMembershipsFromRoomAndMembership(ctx context.Context, txn *sql.Tx, roomNID types.RoomNID, membership MembershipState, localOnly bool) (eventNIDs []types.EventNID, err error)
 	UpdateMembership(ctx context.Context, txn *sql.Tx, roomNID types.RoomNID, targetUserNID types.EventStateKeyNID, senderUserNID types.EventStateKeyNID, membership MembershipState, eventNID types.EventNID, forgotten bool) error
-	SelectRoomsWithMembership(ctx context.Context, userID types.EventStateKeyNID, membershipState MembershipState) ([]types.RoomNID, error)
+	SelectRoomsWithMembership(ctx context.Context, txn *sql.Tx, userID types.EventStateKeyNID, membershipState MembershipState) ([]types.RoomNID, error)
 	// SelectJoinedUsersSetForRooms returns the set of all users in the rooms who are joined to any of these rooms, along with the
 	// counts of how many rooms they are joined.
-	SelectJoinedUsersSetForRooms(ctx context.Context, roomNIDs []types.RoomNID) (map[types.EventStateKeyNID]int, error)
-	SelectKnownUsers(ctx context.Context, userID types.EventStateKeyNID, searchString string, limit int) ([]string, error)
+	SelectJoinedUsersSetForRooms(ctx context.Context, txn *sql.Tx, roomNIDs []types.RoomNID) (map[types.EventStateKeyNID]int, error)
+	SelectKnownUsers(ctx context.Context, txn *sql.Tx, userID types.EventStateKeyNID, searchString string, limit int) ([]string, error)
 	UpdateForgetMembership(ctx context.Context, txn *sql.Tx, roomNID types.RoomNID, targetUserNID types.EventStateKeyNID, forget bool) error
-	SelectLocalServerInRoom(ctx context.Context, roomNID types.RoomNID) (bool, error)
-	SelectServerInRoom(ctx context.Context, roomNID types.RoomNID, serverName gomatrixserverlib.ServerName) (bool, error)
+	SelectLocalServerInRoom(ctx context.Context, txn *sql.Tx, roomNID types.RoomNID) (bool, error)
+	SelectServerInRoom(ctx context.Context, txn *sql.Tx, roomNID types.RoomNID, serverName gomatrixserverlib.ServerName) (bool, error)
 }
 
 type Published interface {
 	UpsertRoomPublished(ctx context.Context, txn *sql.Tx, roomID string, published bool) (err error)
-	SelectPublishedFromRoomID(ctx context.Context, roomID string) (published bool, err error)
-	SelectAllPublishedRooms(ctx context.Context, published bool) ([]string, error)
+	SelectPublishedFromRoomID(ctx context.Context, txn *sql.Tx, roomID string) (published bool, err error)
+	SelectAllPublishedRooms(ctx context.Context, txn *sql.Tx, published bool) ([]string, error)
 }
 
 type RedactionInfo struct {