diff --git a/src/github.com/matrix-org/dendrite/clientapi/auth/storage/accounts/membership_table.go b/src/github.com/matrix-org/dendrite/clientapi/auth/storage/accounts/membership_table.go
index 42922743b..9652cdac7 100644
--- a/src/github.com/matrix-org/dendrite/clientapi/auth/storage/accounts/membership_table.go
+++ b/src/github.com/matrix-org/dendrite/clientapi/auth/storage/accounts/membership_table.go
@@ -44,9 +44,6 @@ const insertMembershipSQL = `
 	ON CONFLICT (localpart, room_id) DO UPDATE SET event_id = EXCLUDED.event_id
 `
 
-const selectMembershipSQL = "" +
-	"SELECT * from account_memberships WHERE localpart = $1 AND room_id = $2"
-
 const selectMembershipsByLocalpartSQL = "" +
 	"SELECT room_id, event_id FROM account_memberships WHERE localpart = $1"
 
diff --git a/src/github.com/matrix-org/dendrite/clientapi/auth/storage/accounts/storage.go b/src/github.com/matrix-org/dendrite/clientapi/auth/storage/accounts/storage.go
index fb98946a0..76b9a4dd9 100644
--- a/src/github.com/matrix-org/dendrite/clientapi/auth/storage/accounts/storage.go
+++ b/src/github.com/matrix-org/dendrite/clientapi/auth/storage/accounts/storage.go
@@ -121,7 +121,8 @@ func (d *Database) SetPartitionOffset(topic string, partition int32, offset int6
 }
 
 // SaveMembership saves the user matching a given localpart as a member of a given
-// room. It also stores the ID of the `join` membership event.
+// room. It also stores the ID of the membership event and a flag on whether the user
+// is still in the room.
 // If a membership already exists between the user and the room, or of the
 // insert fails, returns the SQL error
 func (d *Database) SaveMembership(localpart string, roomID string, eventID string, txn *sql.Tx) error {
@@ -156,23 +157,19 @@ func (d *Database) UpdateMemberships(eventsToAdd []gomatrixserverlib.Event, idsT
 	})
 }
 
-// GetMembershipsByLocalpart returns an array containing the IDs of all the rooms
-// a user matching a given localpart is a member of
+// GetMembershipsByLocalpart returns an array containing the memberships for all
+// the rooms a user matching a given localpart is a member of
 // If no membership match the given localpart, returns an empty array
 // If there was an issue during the retrieval, returns the SQL error
 func (d *Database) GetMembershipsByLocalpart(localpart string) (memberships []authtypes.Membership, err error) {
 	return d.memberships.selectMembershipsByLocalpart(localpart)
 }
 
-// UpdateMembership update the "join" membership event ID of a membership.
-// This is useful in case of membership upgrade (e.g. profile update)
-// If there was an issue during the update, returns the SQL error
-func (d *Database) UpdateMembership(oldEventID string, newEventID string) error {
-	return d.memberships.updateMembershipByEventID(oldEventID, newEventID)
-}
-
-// newMembership will save a new membership in the database if the given state
-// event is a "join" membership event
+// newMembership will save a new membership in the database, with a flag on whether
+// the user is still in the room. This flag is set to true if the given state
+// event is a "join" membership event and false if the event is a "leave" or "ban"
+// membership. If the event isn't a m.room.member event with one of these three
+// values, does nothing.
 // If the event isn't a "join" membership event, does nothing
 // If an error occurred, returns it
 func (d *Database) newMembership(ev gomatrixserverlib.Event, txn *sql.Tx) error {
diff --git a/src/github.com/matrix-org/dendrite/clientapi/readers/memberships.go b/src/github.com/matrix-org/dendrite/clientapi/readers/memberships.go
new file mode 100644
index 000000000..c734e3b34
--- /dev/null
+++ b/src/github.com/matrix-org/dendrite/clientapi/readers/memberships.go
@@ -0,0 +1,55 @@
+// Copyright 2017 Vector Creations Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package readers
+
+import (
+	"net/http"
+
+	"github.com/matrix-org/dendrite/clientapi/auth/authtypes"
+	"github.com/matrix-org/dendrite/clientapi/auth/storage/accounts"
+	"github.com/matrix-org/dendrite/clientapi/httputil"
+	"github.com/matrix-org/dendrite/clientapi/jsonerror"
+	"github.com/matrix-org/dendrite/common/config"
+	"github.com/matrix-org/dendrite/roomserver/api"
+	"github.com/matrix-org/util"
+)
+
+// GetMemberships implements GET /rooms/{roomId}/members
+func GetMemberships(
+	req *http.Request, device *authtypes.Device, roomID string,
+	accountDB *accounts.Database, cfg config.Dendrite,
+	queryAPI api.RoomserverQueryAPI,
+) util.JSONResponse {
+	queryReq := api.QueryMembershipsForRoomRequest{
+		RoomID: roomID,
+		Sender: device.UserID,
+	}
+	var queryRes api.QueryMembershipsForRoomResponse
+	if err := queryAPI.QueryMembershipsForRoom(&queryReq, &queryRes); err != nil {
+		return httputil.LogThenError(req, err)
+	}
+
+	if !queryRes.HasBeenInRoom {
+		return util.JSONResponse{
+			Code: 403,
+			JSON: jsonerror.Forbidden("You aren't a member of the room and weren't previously a member of the room."),
+		}
+	}
+
+	return util.JSONResponse{
+		Code: 200,
+		JSON: queryRes.JoinEvents,
+	}
+}
diff --git a/src/github.com/matrix-org/dendrite/clientapi/routing/routing.go b/src/github.com/matrix-org/dendrite/clientapi/routing/routing.go
index eb84b2a9e..8a5799c0e 100644
--- a/src/github.com/matrix-org/dendrite/clientapi/routing/routing.go
+++ b/src/github.com/matrix-org/dendrite/clientapi/routing/routing.go
@@ -313,6 +313,13 @@ func Setup(
 		}),
 	)
 
+	r0mux.Handle("/rooms/{roomID}/members",
+		common.MakeAuthAPI("rooms_members", deviceDB, func(req *http.Request, device *authtypes.Device) util.JSONResponse {
+			vars := mux.Vars(req)
+			return readers.GetMemberships(req, device, vars["roomID"], accountDB, cfg, queryAPI)
+		}),
+	)
+
 	r0mux.Handle("/rooms/{roomID}/read_markers",
 		common.MakeAPI("rooms_read_markers", func(req *http.Request) util.JSONResponse {
 			// TODO: return the read_markers.
diff --git a/src/github.com/matrix-org/dendrite/common/sql.go b/src/github.com/matrix-org/dendrite/common/sql.go
index cabbe6662..c2fb753fc 100644
--- a/src/github.com/matrix-org/dendrite/common/sql.go
+++ b/src/github.com/matrix-org/dendrite/common/sql.go
@@ -18,6 +18,24 @@ import (
 	"database/sql"
 )
 
+// A Transaction is something that can be committed or rolledback.
+type Transaction interface {
+	// Commit the transaction
+	Commit() error
+	// Rollback the transaction.
+	Rollback() error
+}
+
+// EndTransaction ends a transaction.
+// If the transaction succeeded then it is committed, otherwise it is rolledback.
+func EndTransaction(txn Transaction, succeeded *bool) {
+	if *succeeded {
+		txn.Commit()
+	} else {
+		txn.Rollback()
+	}
+}
+
 // WithTransaction runs a block of code passing in an SQL transaction
 // If the code returns an error or panics then the transactions is rolledback
 // Otherwise the transaction is committed.
@@ -26,16 +44,25 @@ func WithTransaction(db *sql.DB, fn func(txn *sql.Tx) error) (err error) {
 	if err != nil {
 		return
 	}
-	defer func() {
-		if r := recover(); r != nil {
-			txn.Rollback()
-			panic(r)
-		} else if err != nil {
-			txn.Rollback()
-		} else {
-			err = txn.Commit()
-		}
-	}()
+	succeeded := false
+	defer EndTransaction(txn, &succeeded)
+
 	err = fn(txn)
+	if err != nil {
+		return
+	}
+
+	succeeded = true
 	return
 }
+
+// TxStmt wraps an SQL stmt inside an optional transaction.
+// If the transaction is nil then it returns the original statement that will
+// run outside of a transaction.
+// Otherwise returns a copy of the statement that will run inside the transaction.
+func TxStmt(transaction *sql.Tx, statement *sql.Stmt) *sql.Stmt {
+	if transaction != nil {
+		statement = transaction.Stmt(statement)
+	}
+	return statement
+}
diff --git a/src/github.com/matrix-org/dendrite/common/test/server.go b/src/github.com/matrix-org/dendrite/common/test/server.go
index d990d4105..8e1af2041 100644
--- a/src/github.com/matrix-org/dendrite/common/test/server.go
+++ b/src/github.com/matrix-org/dendrite/common/test/server.go
@@ -94,6 +94,8 @@ func StartProxy(bindAddr string, cfg *config.Dendrite) (*exec.Cmd, chan error) {
 		"--sync-api-server-url", "http://" + string(cfg.Listen.SyncAPI),
 		"--client-api-server-url", "http://" + string(cfg.Listen.ClientAPI),
 		"--media-api-server-url", "http://" + string(cfg.Listen.MediaAPI),
+		"--tls-cert", "server.crt",
+		"--tls-key", "server.key",
 	}
 	return CreateBackgroundCommand(
 		filepath.Join(filepath.Dir(os.Args[0]), "client-api-proxy"),
diff --git a/src/github.com/matrix-org/dendrite/federationsender/storage/joined_hosts_table.go b/src/github.com/matrix-org/dendrite/federationsender/storage/joined_hosts_table.go
index 7ba1b0b07..fffcc7f3f 100644
--- a/src/github.com/matrix-org/dendrite/federationsender/storage/joined_hosts_table.go
+++ b/src/github.com/matrix-org/dendrite/federationsender/storage/joined_hosts_table.go
@@ -18,6 +18,7 @@ import (
 	"database/sql"
 
 	"github.com/lib/pq"
+	"github.com/matrix-org/dendrite/common"
 	"github.com/matrix-org/dendrite/federationsender/types"
 	"github.com/matrix-org/gomatrixserverlib"
 )
@@ -79,18 +80,18 @@ func (s *joinedHostsStatements) prepare(db *sql.DB) (err error) {
 func (s *joinedHostsStatements) insertJoinedHosts(
 	txn *sql.Tx, roomID, eventID string, serverName gomatrixserverlib.ServerName,
 ) error {
-	_, err := txn.Stmt(s.insertJoinedHostsStmt).Exec(roomID, eventID, serverName)
+	_, err := common.TxStmt(txn, s.insertJoinedHostsStmt).Exec(roomID, eventID, serverName)
 	return err
 }
 
 func (s *joinedHostsStatements) deleteJoinedHosts(txn *sql.Tx, eventIDs []string) error {
-	_, err := txn.Stmt(s.deleteJoinedHostsStmt).Exec(pq.StringArray(eventIDs))
+	_, err := common.TxStmt(txn, s.deleteJoinedHostsStmt).Exec(pq.StringArray(eventIDs))
 	return err
 }
 
 func (s *joinedHostsStatements) selectJoinedHosts(txn *sql.Tx, roomID string,
 ) ([]types.JoinedHost, error) {
-	rows, err := txn.Stmt(s.selectJoinedHostsStmt).Query(roomID)
+	rows, err := common.TxStmt(txn, s.selectJoinedHostsStmt).Query(roomID)
 	if err != nil {
 		return nil, err
 	}
diff --git a/src/github.com/matrix-org/dendrite/federationsender/storage/room_table.go b/src/github.com/matrix-org/dendrite/federationsender/storage/room_table.go
index daac7ddf4..bcc0bb1df 100644
--- a/src/github.com/matrix-org/dendrite/federationsender/storage/room_table.go
+++ b/src/github.com/matrix-org/dendrite/federationsender/storage/room_table.go
@@ -16,6 +16,8 @@ package storage
 
 import (
 	"database/sql"
+
+	"github.com/matrix-org/dendrite/common"
 )
 
 const roomSchema = `
@@ -65,7 +67,7 @@ func (s *roomStatements) prepare(db *sql.DB) (err error) {
 // insertRoom inserts the room if it didn't already exist.
 // If the room didn't exist then last_event_id is set to the empty string.
 func (s *roomStatements) insertRoom(txn *sql.Tx, roomID string) error {
-	_, err := txn.Stmt(s.insertRoomStmt).Exec(roomID)
+	_, err := common.TxStmt(txn, s.insertRoomStmt).Exec(roomID)
 	return err
 }
 
@@ -74,7 +76,7 @@ func (s *roomStatements) insertRoom(txn *sql.Tx, roomID string) error {
 // exists by calling insertRoom first.
 func (s *roomStatements) selectRoomForUpdate(txn *sql.Tx, roomID string) (string, error) {
 	var lastEventID string
-	err := txn.Stmt(s.selectRoomForUpdateStmt).QueryRow(roomID).Scan(&lastEventID)
+	err := common.TxStmt(txn, s.selectRoomForUpdateStmt).QueryRow(roomID).Scan(&lastEventID)
 	if err != nil {
 		return "", err
 	}
@@ -84,6 +86,6 @@ func (s *roomStatements) selectRoomForUpdate(txn *sql.Tx, roomID string) (string
 // updateRoom updates the last_event_id for the room. selectRoomForUpdate should
 // have already been called earlier within the transaction.
 func (s *roomStatements) updateRoom(txn *sql.Tx, roomID, lastEventID string) error {
-	_, err := txn.Stmt(s.updateRoomStmt).Exec(roomID, lastEventID)
+	_, err := common.TxStmt(txn, s.updateRoomStmt).Exec(roomID, lastEventID)
 	return err
 }
diff --git a/src/github.com/matrix-org/dendrite/roomserver/api/input.go b/src/github.com/matrix-org/dendrite/roomserver/api/input.go
index 558eb28c4..cbe7399ba 100644
--- a/src/github.com/matrix-org/dendrite/roomserver/api/input.go
+++ b/src/github.com/matrix-org/dendrite/roomserver/api/input.go
@@ -68,9 +68,17 @@ type InputRoomEvent struct {
 	SendAsServer string `json:"send_as_server"`
 }
 
+// InputInviteEvent is a matrix invite event received over federation without
+// the usual context a matrix room event would have. We usually do not have
+// access to the events needed to check the event auth rules for the invite.
+type InputInviteEvent struct {
+	Event gomatrixserverlib.Event `json:"event"`
+}
+
 // InputRoomEventsRequest is a request to InputRoomEvents
 type InputRoomEventsRequest struct {
-	InputRoomEvents []InputRoomEvent `json:"input_room_events"`
+	InputRoomEvents   []InputRoomEvent   `json:"input_room_events"`
+	InputInviteEvents []InputInviteEvent `json:"input_invite_events"`
 }
 
 // InputRoomEventsResponse is a response to InputRoomEvents
diff --git a/src/github.com/matrix-org/dendrite/roomserver/api/query.go b/src/github.com/matrix-org/dendrite/roomserver/api/query.go
index 6e6a838a9..f07da59e5 100644
--- a/src/github.com/matrix-org/dendrite/roomserver/api/query.go
+++ b/src/github.com/matrix-org/dendrite/roomserver/api/query.go
@@ -100,6 +100,23 @@ type QueryEventsByIDResponse struct {
 	Events []gomatrixserverlib.Event `json:"events"`
 }
 
+// QueryMembershipsForRoomRequest is a request to QueryMembershipsForRoom
+type QueryMembershipsForRoomRequest struct {
+	// ID of the room to fetch memberships from
+	RoomID string `json:"room_id"`
+	// ID of the user sending the request
+	Sender string `json:"sender"`
+}
+
+// QueryMembershipsForRoomResponse is a response to QueryMembershipsForRoom
+type QueryMembershipsForRoomResponse struct {
+	// The "m.room.member" events (of "join" membership) in the client format
+	JoinEvents []gomatrixserverlib.ClientEvent `json:"join_events"`
+	// True if the user has been in room before and has either stayed in it or
+	// left it.
+	HasBeenInRoom bool `json:"has_been_in_room"`
+}
+
 // RoomserverQueryAPI is used to query information from the room server.
 type RoomserverQueryAPI interface {
 	// Query the latest events and state for a room from the room server.
@@ -119,6 +136,12 @@ type RoomserverQueryAPI interface {
 		request *QueryEventsByIDRequest,
 		response *QueryEventsByIDResponse,
 	) error
+
+	// Query a list of membership events for a room
+	QueryMembershipsForRoom(
+		request *QueryMembershipsForRoomRequest,
+		response *QueryMembershipsForRoomResponse,
+	) error
 }
 
 // RoomserverQueryLatestEventsAndStatePath is the HTTP path for the QueryLatestEventsAndState API.
@@ -130,6 +153,9 @@ const RoomserverQueryStateAfterEventsPath = "/api/roomserver/queryStateAfterEven
 // RoomserverQueryEventsByIDPath is the HTTP path for the QueryEventsByID API.
 const RoomserverQueryEventsByIDPath = "/api/roomserver/queryEventsByID"
 
+// RoomserverQueryMembershipsForRoomPath is the HTTP path for the QueryMembershipsForRoom API
+const RoomserverQueryMembershipsForRoomPath = "/api/roomserver/queryMembershipsForRoom"
+
 // NewRoomserverQueryAPIHTTP creates a RoomserverQueryAPI implemented by talking to a HTTP POST API.
 // If httpClient is nil then it uses the http.DefaultClient
 func NewRoomserverQueryAPIHTTP(roomserverURL string, httpClient *http.Client) RoomserverQueryAPI {
@@ -171,6 +197,15 @@ func (h *httpRoomserverQueryAPI) QueryEventsByID(
 	return postJSON(h.httpClient, apiURL, request, response)
 }
 
+// QueryMembershipsForRoom implements RoomserverQueryAPI
+func (h *httpRoomserverQueryAPI) QueryMembershipsForRoom(
+	request *QueryMembershipsForRoomRequest,
+	response *QueryMembershipsForRoomResponse,
+) error {
+	apiURL := h.roomserverURL + RoomserverQueryMembershipsForRoomPath
+	return postJSON(h.httpClient, apiURL, request, response)
+}
+
 func postJSON(httpClient *http.Client, apiURL string, request, response interface{}) error {
 	jsonBytes, err := json.Marshal(request)
 	if err != nil {
diff --git a/src/github.com/matrix-org/dendrite/roomserver/input/events.go b/src/github.com/matrix-org/dendrite/roomserver/input/events.go
index c1eee4c96..82b4652e6 100644
--- a/src/github.com/matrix-org/dendrite/roomserver/input/events.go
+++ b/src/github.com/matrix-org/dendrite/roomserver/input/events.go
@@ -15,6 +15,9 @@
 package input
 
 import (
+	"fmt"
+
+	"github.com/matrix-org/dendrite/common"
 	"github.com/matrix-org/dendrite/roomserver/api"
 	"github.com/matrix-org/dendrite/roomserver/state"
 	"github.com/matrix-org/dendrite/roomserver/types"
@@ -39,6 +42,8 @@ type RoomEventDatabase interface {
 	GetLatestEventsForUpdate(roomNID types.RoomNID) (updater types.RoomRecentEventsUpdater, err error)
 	// Lookup the string event IDs for a list of numeric event IDs
 	EventIDs(eventNIDs []types.EventNID) (map[types.EventNID]string, error)
+	// Build a membership updater for the target user in a room.
+	MembershipUpdater(roomID, targerUserID string) (types.MembershipUpdater, error)
 }
 
 // OutputRoomEventWriter has the APIs needed to write an event to the output logs.
@@ -103,13 +108,64 @@ func processRoomEvent(db RoomEventDatabase, ow OutputRoomEventWriter, input api.
 		return err
 	}
 
-	// TODO:
-	//  * Caculate the new current state for the room if the forward extremities have changed.
-	//  * Work out the delta between the new current state and the previous current state.
-	//  * Work out the visibility of the event.
-	//  * Write a message to the output logs containing:
-	//      - The event itself
-	//      - The visiblity of the event, i.e. who is allowed to see the event.
-	//      - The changes to the current state of the room.
+	return nil
+}
+
+func processInviteEvent(db RoomEventDatabase, ow OutputRoomEventWriter, input api.InputInviteEvent) (err error) {
+	if input.Event.StateKey() == nil {
+		return fmt.Errorf("invite must be a state event")
+	}
+
+	roomID := input.Event.RoomID()
+	targetUserID := *input.Event.StateKey()
+
+	updater, err := db.MembershipUpdater(roomID, targetUserID)
+	if err != nil {
+		return err
+	}
+	succeeded := false
+	defer common.EndTransaction(updater, &succeeded)
+
+	if updater.IsJoin() {
+		// If the user is joined to the room then that takes precedence over this
+		// invite event. It makes little sense to move a user that is already
+		// joined to the room into the invite state.
+		// This could plausibly happen if an invite request raced with a join
+		// request for a user. For example if a user was invited to a public
+		// room and they joined the room at the same time as the invite was sent.
+		// The other way this could plausibly happen is if an invite raced with
+		// a kick. For example if a user was kicked from a room in error and in
+		// response someone else in the room re-invited them then it is possible
+		// for the invite request to race with the leave event so that the
+		// target receives invite before it learns that it has been kicked.
+		// There are a few ways this could be plausibly handled in the roomserver.
+		// 1) Store the invite, but mark it as retired. That will result in the
+		//    permanent rejection of that invite event. So even if the target
+		//    user leaves the room and the invite is retransmitted it will be
+		//    ignored. However a new invite with a new event ID would still be
+		//    accepted.
+		// 2) Silently discard the invite event. This means that if the event
+		//    was retransmitted at a later date after the target user had left
+		//    the room we would accept the invite. However since we hadn't told
+		//    the sending server that the invite had been discarded it would
+		//    have no reason to attempt to retry.
+		// 3) Signal the sending server that the user is already joined to the
+		//    room.
+		// For now we will implement option 2. Since in the abesence of a retry
+		// mechanism it will be equivalent to option 1, and we don't have a
+		// signalling mechanism to implement option 3.
+		return nil
+	}
+
+	outputUpdates, err := updateToInviteMembership(updater, &input.Event, nil)
+	if err != nil {
+		return err
+	}
+
+	if err = ow.WriteOutputEvents(roomID, outputUpdates); err != nil {
+		return err
+	}
+
+	succeeded = true
 	return nil
 }
diff --git a/src/github.com/matrix-org/dendrite/roomserver/input/input.go b/src/github.com/matrix-org/dendrite/roomserver/input/input.go
index 210abfa29..17e94599e 100644
--- a/src/github.com/matrix-org/dendrite/roomserver/input/input.go
+++ b/src/github.com/matrix-org/dendrite/roomserver/input/input.go
@@ -61,6 +61,11 @@ func (r *RoomserverInputAPI) InputRoomEvents(
 			return err
 		}
 	}
+	for i := range request.InputInviteEvents {
+		if err := processInviteEvent(r.DB, r, request.InputInviteEvents[i]); err != nil {
+			return err
+		}
+	}
 	return nil
 }
 
diff --git a/src/github.com/matrix-org/dendrite/roomserver/input/latest_events.go b/src/github.com/matrix-org/dendrite/roomserver/input/latest_events.go
index 9328ecf3b..d9aa2b455 100644
--- a/src/github.com/matrix-org/dendrite/roomserver/input/latest_events.go
+++ b/src/github.com/matrix-org/dendrite/roomserver/input/latest_events.go
@@ -17,6 +17,7 @@ package input
 import (
 	"bytes"
 
+	"github.com/matrix-org/dendrite/common"
 	"github.com/matrix-org/dendrite/roomserver/api"
 	"github.com/matrix-org/dendrite/roomserver/state"
 	"github.com/matrix-org/dendrite/roomserver/types"
@@ -52,25 +53,19 @@ func updateLatestEvents(
 	if err != nil {
 		return
 	}
-	defer func() {
-		if err == nil {
-			// Commit if there wasn't an error.
-			// Set the returned err value if we encounter an error committing.
-			// This only works because err is a named return.
-			err = updater.Commit()
-		} else {
-			// Ignore any error we get rolling back since we don't want to
-			// clobber the current error
-			// TODO: log the error here.
-			updater.Rollback()
-		}
-	}()
+	succeeded := false
+	defer common.EndTransaction(updater, &succeeded)
 
 	u := latestEventsUpdater{
 		db: db, updater: updater, ow: ow, roomNID: roomNID,
 		stateAtEvent: stateAtEvent, event: event, sendAsServer: sendAsServer,
 	}
-	return u.doUpdateLatestEvents()
+	if err = u.doUpdateLatestEvents(); err != nil {
+		return err
+	}
+
+	succeeded = true
+	return
 }
 
 // latestEventsUpdater tracks the state used to update the latest events in the
diff --git a/src/github.com/matrix-org/dendrite/roomserver/input/membership.go b/src/github.com/matrix-org/dendrite/roomserver/input/membership.go
index f306697ff..6eeb0914d 100644
--- a/src/github.com/matrix-org/dendrite/roomserver/input/membership.go
+++ b/src/github.com/matrix-org/dendrite/roomserver/input/membership.go
@@ -95,10 +95,9 @@ func updateMembership(
 			return nil, err
 		}
 	}
-	if old == new {
+	if old == new && new != "join" {
 		// If the membership is the same then nothing changed and we can return
-		// immediately. This should help speed up processing for display name
-		// changes where the membership is "join" both before and after.
+		// immediately, unless it's a "join" update (e.g. profile update).
 		return updates, nil
 	}
 
@@ -152,16 +151,21 @@ func updateToInviteMembership(
 func updateToJoinMembership(
 	mu types.MembershipUpdater, add *gomatrixserverlib.Event, updates []api.OutputEvent,
 ) ([]api.OutputEvent, error) {
-	// If the user is already marked as being joined then we can return immediately.
-	// TODO: Is this code reachable given the "old != new" guard in updateMembership?
+	// If the user is already marked as being joined, we call SetToJoin to update
+	// the event ID then we can return immediately. Retired is ignored as there
+	// is no invite event to retire.
 	if mu.IsJoin() {
+		_, err := mu.SetToJoin(add.Sender(), add.EventID(), true)
+		if err != nil {
+			return nil, err
+		}
 		return updates, nil
 	}
 	// When we mark a user as being joined we will invalidate any invites that
 	// are active for that user. We notify the consumers that the invites have
 	// been retired using a special event, even though they could infer this
 	// by studying the state changes in the room event stream.
-	retired, err := mu.SetToJoin(add.Sender())
+	retired, err := mu.SetToJoin(add.Sender(), add.EventID(), false)
 	if err != nil {
 		return nil, err
 	}
@@ -194,7 +198,7 @@ func updateToLeaveMembership(
 	// are active for that user. We notify the consumers that the invites have
 	// been retired using a special event, even though they could infer this
 	// by studying the state changes in the room event stream.
-	retired, err := mu.SetToLeave(add.Sender())
+	retired, err := mu.SetToLeave(add.Sender(), add.EventID())
 	if err != nil {
 		return nil, err
 	}
diff --git a/src/github.com/matrix-org/dendrite/roomserver/query/query.go b/src/github.com/matrix-org/dendrite/roomserver/query/query.go
index 30b695fb4..84f5d44c3 100644
--- a/src/github.com/matrix-org/dendrite/roomserver/query/query.go
+++ b/src/github.com/matrix-org/dendrite/roomserver/query/query.go
@@ -52,6 +52,13 @@ type RoomserverQueryAPIDatabase interface {
 	// Remove a given room alias.
 	// Returns an error if there was a problem talking to the database.
 	RemoveRoomAlias(alias string) error
+	// Lookup the join events for all members in a room as requested by a given
+	// user. If the user is currently in the room, returns the room's current
+	// members, if not returns an empty array (TODO: Fix it)
+	// If the user requesting the list of members has never been in the room,
+	// returns nil.
+	// If there was an issue retrieving the events, returns an error.
+	GetMembershipEvents(roomNID types.RoomNID, requestSenderUserID string) (events []types.Event, err error)
 }
 
 // RoomserverQueryAPI is an implementation of api.RoomserverQueryAPI
@@ -182,6 +189,37 @@ func (r *RoomserverQueryAPI) loadEvents(eventNIDs []types.EventNID) ([]gomatrixs
 	return result, nil
 }
 
+// QueryMembershipsForRoom implements api.RoomserverQueryAPI
+func (r *RoomserverQueryAPI) QueryMembershipsForRoom(
+	request *api.QueryMembershipsForRoomRequest,
+	response *api.QueryMembershipsForRoomResponse,
+) error {
+	roomNID, err := r.DB.RoomNID(request.RoomID)
+	if err != nil {
+		return err
+	}
+
+	events, err := r.DB.GetMembershipEvents(roomNID, request.Sender)
+	if err != nil {
+		return nil
+	}
+
+	if events == nil {
+		response.HasBeenInRoom = false
+		response.JoinEvents = nil
+		return nil
+	}
+
+	response.HasBeenInRoom = true
+	response.JoinEvents = []gomatrixserverlib.ClientEvent{}
+	for _, event := range events {
+		clientEvent := gomatrixserverlib.ToClientEvent(event.Event, gomatrixserverlib.FormatAll)
+		response.JoinEvents = append(response.JoinEvents, clientEvent)
+	}
+
+	return nil
+}
+
 // SetupHTTP adds the RoomserverQueryAPI handlers to the http.ServeMux.
 func (r *RoomserverQueryAPI) SetupHTTP(servMux *http.ServeMux) {
 	servMux.Handle(
@@ -226,4 +264,18 @@ func (r *RoomserverQueryAPI) SetupHTTP(servMux *http.ServeMux) {
 			return util.JSONResponse{Code: 200, JSON: &response}
 		}),
 	)
+	servMux.Handle(
+		api.RoomserverQueryMembershipsForRoomPath,
+		common.MakeAPI("queryMembershipsForRoom", func(req *http.Request) util.JSONResponse {
+			var request api.QueryMembershipsForRoomRequest
+			var response api.QueryMembershipsForRoomResponse
+			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
+				return util.ErrorResponse(err)
+			}
+			if err := r.QueryMembershipsForRoom(&request, &response); err != nil {
+				return util.ErrorResponse(err)
+			}
+			return util.JSONResponse{Code: 200, JSON: &response}
+		}),
+	)
 }
diff --git a/src/github.com/matrix-org/dendrite/roomserver/storage/event_state_keys_table.go b/src/github.com/matrix-org/dendrite/roomserver/storage/event_state_keys_table.go
index d30e45815..b06f5b2a5 100644
--- a/src/github.com/matrix-org/dendrite/roomserver/storage/event_state_keys_table.go
+++ b/src/github.com/matrix-org/dendrite/roomserver/storage/event_state_keys_table.go
@@ -18,6 +18,7 @@ import (
 	"database/sql"
 
 	"github.com/lib/pq"
+	"github.com/matrix-org/dendrite/common"
 	"github.com/matrix-org/dendrite/roomserver/types"
 )
 
@@ -58,10 +59,22 @@ const bulkSelectEventStateKeyNIDSQL = "" +
 	"SELECT event_state_key, event_state_key_nid FROM roomserver_event_state_keys" +
 	" WHERE event_state_key = ANY($1)"
 
+const selectEventStateKeySQL = "" +
+	"SELECT event_state_key FROM roomserver_event_state_keys" +
+	" WHERE event_state_key_nid = $1"
+
+// Bulk lookup from numeric ID to string state key for that state key.
+// Takes an array of strings as the query parameter.
+const bulkSelectEventStateKeySQL = "" +
+	"SELECT event_state_key, event_state_key_nid FROM roomserver_event_state_keys" +
+	" WHERE event_state_key_nid = ANY($1)"
+
 type eventStateKeyStatements struct {
 	insertEventStateKeyNIDStmt     *sql.Stmt
 	selectEventStateKeyNIDStmt     *sql.Stmt
+	selectEventStateKeyStmt        *sql.Stmt
 	bulkSelectEventStateKeyNIDStmt *sql.Stmt
+	bulkSelectEventStateKeyStmt    *sql.Stmt
 }
 
 func (s *eventStateKeyStatements) prepare(db *sql.DB) (err error) {
@@ -72,27 +85,21 @@ func (s *eventStateKeyStatements) prepare(db *sql.DB) (err error) {
 	return statementList{
 		{&s.insertEventStateKeyNIDStmt, insertEventStateKeyNIDSQL},
 		{&s.selectEventStateKeyNIDStmt, selectEventStateKeyNIDSQL},
+		{&s.selectEventStateKeyStmt, selectEventStateKeySQL},
 		{&s.bulkSelectEventStateKeyNIDStmt, bulkSelectEventStateKeyNIDSQL},
+		{&s.bulkSelectEventStateKeyStmt, bulkSelectEventStateKeySQL},
 	}.prepare(db)
 }
 
 func (s *eventStateKeyStatements) insertEventStateKeyNID(txn *sql.Tx, eventStateKey string) (types.EventStateKeyNID, error) {
 	var eventStateKeyNID int64
-	stmt := s.insertEventStateKeyNIDStmt
-	if txn != nil {
-		stmt = txn.Stmt(stmt)
-	}
-	err := stmt.QueryRow(eventStateKey).Scan(&eventStateKeyNID)
+	err := common.TxStmt(txn, s.insertEventStateKeyNIDStmt).QueryRow(eventStateKey).Scan(&eventStateKeyNID)
 	return types.EventStateKeyNID(eventStateKeyNID), err
 }
 
 func (s *eventStateKeyStatements) selectEventStateKeyNID(txn *sql.Tx, eventStateKey string) (types.EventStateKeyNID, error) {
 	var eventStateKeyNID int64
-	stmt := s.selectEventStateKeyNIDStmt
-	if txn != nil {
-		stmt = txn.Stmt(stmt)
-	}
-	err := stmt.QueryRow(eventStateKey).Scan(&eventStateKeyNID)
+	err := common.TxStmt(txn, s.selectEventStateKeyNIDStmt).QueryRow(eventStateKey).Scan(&eventStateKeyNID)
 	return types.EventStateKeyNID(eventStateKeyNID), err
 }
 
@@ -114,3 +121,32 @@ func (s *eventStateKeyStatements) bulkSelectEventStateKeyNID(eventStateKeys []st
 	}
 	return result, nil
 }
+
+func (s *eventStateKeyStatements) selectEventStateKey(txn *sql.Tx, eventStateKeyNID types.EventStateKeyNID) (string, error) {
+	var eventStateKey string
+	err := common.TxStmt(txn, s.selectEventStateKeyStmt).QueryRow(eventStateKeyNID).Scan(&eventStateKey)
+	return eventStateKey, err
+}
+
+func (s *eventStateKeyStatements) bulkSelectEventStateKey(eventStateKeyNIDs []types.EventStateKeyNID) (map[types.EventStateKeyNID]string, error) {
+	var nIDs pq.Int64Array
+	for i := range eventStateKeyNIDs {
+		nIDs[i] = int64(eventStateKeyNIDs[i])
+	}
+	rows, err := s.bulkSelectEventStateKeyStmt.Query(nIDs)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	result := make(map[types.EventStateKeyNID]string, len(eventStateKeyNIDs))
+	for rows.Next() {
+		var stateKey string
+		var stateKeyNID int64
+		if err := rows.Scan(&stateKey, &stateKeyNID); err != nil {
+			return nil, err
+		}
+		result[types.EventStateKeyNID(stateKeyNID)] = stateKey
+	}
+	return result, nil
+}
diff --git a/src/github.com/matrix-org/dendrite/roomserver/storage/events_table.go b/src/github.com/matrix-org/dendrite/roomserver/storage/events_table.go
index b6db15c82..2d2b85625 100644
--- a/src/github.com/matrix-org/dendrite/roomserver/storage/events_table.go
+++ b/src/github.com/matrix-org/dendrite/roomserver/storage/events_table.go
@@ -19,6 +19,7 @@ import (
 	"fmt"
 
 	"github.com/lib/pq"
+	"github.com/matrix-org/dendrite/common"
 	"github.com/matrix-org/dendrite/roomserver/types"
 	"github.com/matrix-org/gomatrixserverlib"
 )
@@ -253,22 +254,22 @@ func (s *eventStatements) updateEventState(eventNID types.EventNID, stateNID typ
 }
 
 func (s *eventStatements) selectEventSentToOutput(txn *sql.Tx, eventNID types.EventNID) (sentToOutput bool, err error) {
-	err = txn.Stmt(s.selectEventSentToOutputStmt).QueryRow(int64(eventNID)).Scan(&sentToOutput)
+	err = common.TxStmt(txn, s.selectEventSentToOutputStmt).QueryRow(int64(eventNID)).Scan(&sentToOutput)
 	return
 }
 
 func (s *eventStatements) updateEventSentToOutput(txn *sql.Tx, eventNID types.EventNID) error {
-	_, err := txn.Stmt(s.updateEventSentToOutputStmt).Exec(int64(eventNID))
+	_, err := common.TxStmt(txn, s.updateEventSentToOutputStmt).Exec(int64(eventNID))
 	return err
 }
 
 func (s *eventStatements) selectEventID(txn *sql.Tx, eventNID types.EventNID) (eventID string, err error) {
-	err = txn.Stmt(s.selectEventIDStmt).QueryRow(int64(eventNID)).Scan(&eventID)
+	err = common.TxStmt(txn, s.selectEventIDStmt).QueryRow(int64(eventNID)).Scan(&eventID)
 	return
 }
 
 func (s *eventStatements) bulkSelectStateAtEventAndReference(txn *sql.Tx, eventNIDs []types.EventNID) ([]types.StateAtEventAndReference, error) {
-	rows, err := txn.Stmt(s.bulkSelectStateAtEventAndReferenceStmt).Query(eventNIDsAsArray(eventNIDs))
+	rows, err := common.TxStmt(txn, s.bulkSelectStateAtEventAndReferenceStmt).Query(eventNIDsAsArray(eventNIDs))
 	if err != nil {
 		return nil, err
 	}
diff --git a/src/github.com/matrix-org/dendrite/roomserver/storage/invite_table.go b/src/github.com/matrix-org/dendrite/roomserver/storage/invite_table.go
index 9e0860b42..8bae2b781 100644
--- a/src/github.com/matrix-org/dendrite/roomserver/storage/invite_table.go
+++ b/src/github.com/matrix-org/dendrite/roomserver/storage/invite_table.go
@@ -17,6 +17,7 @@ package storage
 import (
 	"database/sql"
 
+	"github.com/matrix-org/dendrite/common"
 	"github.com/matrix-org/dendrite/roomserver/types"
 )
 
@@ -94,7 +95,7 @@ func (s *inviteStatements) insertInviteEvent(
 	targetUserNID, senderUserNID types.EventStateKeyNID,
 	inviteEventJSON []byte,
 ) (bool, error) {
-	result, err := txn.Stmt(s.insertInviteEventStmt).Exec(
+	result, err := common.TxStmt(txn, s.insertInviteEventStmt).Exec(
 		inviteEventID, roomNID, targetUserNID, senderUserNID, inviteEventJSON,
 	)
 	if err != nil {
@@ -110,7 +111,7 @@ func (s *inviteStatements) insertInviteEvent(
 func (s *inviteStatements) updateInviteRetired(
 	txn *sql.Tx, roomNID types.RoomNID, targetUserNID types.EventStateKeyNID,
 ) ([]string, error) {
-	rows, err := txn.Stmt(s.updateInviteRetiredStmt).Query(roomNID, targetUserNID)
+	rows, err := common.TxStmt(txn, s.updateInviteRetiredStmt).Query(roomNID, targetUserNID)
 	if err != nil {
 		return nil, err
 	}
diff --git a/src/github.com/matrix-org/dendrite/roomserver/storage/membership_table.go b/src/github.com/matrix-org/dendrite/roomserver/storage/membership_table.go
index 725e5b8d9..6edc7a528 100644
--- a/src/github.com/matrix-org/dendrite/roomserver/storage/membership_table.go
+++ b/src/github.com/matrix-org/dendrite/roomserver/storage/membership_table.go
@@ -17,6 +17,7 @@ package storage
 import (
 	"database/sql"
 
+	"github.com/matrix-org/dendrite/common"
 	"github.com/matrix-org/dendrite/roomserver/types"
 )
 
@@ -33,7 +34,7 @@ const membershipSchema = `
 -- and the room state tables.
 -- This table is updated in one of 3 ways:
 --   1) The membership of a user changes within the current state of the room.
---   2) An invite is received outside of a room over federation. 
+--   2) An invite is received outside of a room over federation.
 --   3) An invite is rejected outside of a room over federation.
 CREATE TABLE IF NOT EXISTS roomserver_membership (
 	room_nid BIGINT NOT NULL,
@@ -46,6 +47,16 @@ CREATE TABLE IF NOT EXISTS roomserver_membership (
 	-- The state the user is in within this room.
 	-- Default value is "membershipStateLeaveOrBan"
 	membership_nid BIGINT NOT NULL DEFAULT 1,
+	-- The numeric ID of the membership event.
+	-- It refers to the join membership event if the membership_nid is join (3),
+	-- and to the leave/ban membership event if the membership_nid is leave or
+	-- ban (1).
+	-- If the membership_nid is invite (2) and the user has been in the room
+	-- before, it will refer to the previous leave/ban membership event, and will
+	-- be equals to 0 (its default) if the user never joined the room before.
+	-- This NID is updated if the join event gets updated (e.g. profile update),
+	-- or if the user leaves/joins the room.
+	event_nid BIGINT NOT NULL DEFAULT 0,
 	UNIQUE (room_nid, target_nid)
 );
 `
@@ -57,18 +68,33 @@ const insertMembershipSQL = "" +
 	" VALUES ($1, $2)" +
 	" ON CONFLICT DO NOTHING"
 
+const selectMembershipFromRoomAndTargetSQL = "" +
+	"SELECT membership_nid, event_nid FROM roomserver_membership" +
+	" WHERE room_nid = $1 AND target_nid = $2"
+
+const selectMembershipsFromRoomAndMembershipSQL = "" +
+	"SELECT event_nid FROM roomserver_membership" +
+	" WHERE room_nid = $1 AND membership_nid = $2"
+
+const selectMembershipsFromRoomSQL = "" +
+	"SELECT membership_nid, event_nid FROM roomserver_membership" +
+	" WHERE room_nid = $1"
+
 const selectMembershipForUpdateSQL = "" +
 	"SELECT membership_nid FROM roomserver_membership" +
 	" WHERE room_nid = $1 AND target_nid = $2 FOR UPDATE"
 
 const updateMembershipSQL = "" +
-	"UPDATE roomserver_membership SET sender_nid = $3, membership_nid = $4" +
+	"UPDATE roomserver_membership SET sender_nid = $3, membership_nid = $4, event_nid = $5" +
 	" WHERE room_nid = $1 AND target_nid = $2"
 
 type membershipStatements struct {
-	insertMembershipStmt          *sql.Stmt
-	selectMembershipForUpdateStmt *sql.Stmt
-	updateMembershipStmt          *sql.Stmt
+	insertMembershipStmt                       *sql.Stmt
+	selectMembershipForUpdateStmt              *sql.Stmt
+	selectMembershipFromRoomAndTargetStmt      *sql.Stmt
+	selectMembershipsFromRoomAndMembershipStmt *sql.Stmt
+	selectMembershipsFromRoomStmt              *sql.Stmt
+	updateMembershipStmt                       *sql.Stmt
 }
 
 func (s *membershipStatements) prepare(db *sql.DB) (err error) {
@@ -80,6 +106,9 @@ func (s *membershipStatements) prepare(db *sql.DB) (err error) {
 	return statementList{
 		{&s.insertMembershipStmt, insertMembershipSQL},
 		{&s.selectMembershipForUpdateStmt, selectMembershipForUpdateSQL},
+		{&s.selectMembershipFromRoomAndTargetStmt, selectMembershipFromRoomAndTargetSQL},
+		{&s.selectMembershipsFromRoomAndMembershipStmt, selectMembershipsFromRoomAndMembershipSQL},
+		{&s.selectMembershipsFromRoomStmt, selectMembershipsFromRoomSQL},
 		{&s.updateMembershipStmt, updateMembershipSQL},
 	}.prepare(db)
 }
@@ -87,25 +116,72 @@ func (s *membershipStatements) prepare(db *sql.DB) (err error) {
 func (s *membershipStatements) insertMembership(
 	txn *sql.Tx, roomNID types.RoomNID, targetUserNID types.EventStateKeyNID,
 ) error {
-	_, err := txn.Stmt(s.insertMembershipStmt).Exec(roomNID, targetUserNID)
+	_, err := common.TxStmt(txn, s.insertMembershipStmt).Exec(roomNID, targetUserNID)
 	return err
 }
 
 func (s *membershipStatements) selectMembershipForUpdate(
 	txn *sql.Tx, roomNID types.RoomNID, targetUserNID types.EventStateKeyNID,
 ) (membership membershipState, err error) {
-	err = txn.Stmt(s.selectMembershipForUpdateStmt).QueryRow(
+	err = common.TxStmt(txn, s.selectMembershipForUpdateStmt).QueryRow(
 		roomNID, targetUserNID,
 	).Scan(&membership)
 	return
 }
 
+func (s *membershipStatements) selectMembershipFromRoomAndTarget(
+	roomNID types.RoomNID, targetUserNID types.EventStateKeyNID,
+) (eventNID types.EventNID, membership membershipState, err error) {
+	err = s.selectMembershipFromRoomAndTargetStmt.QueryRow(
+		roomNID, targetUserNID,
+	).Scan(&membership, &eventNID)
+	return
+}
+
+func (s *membershipStatements) selectMembershipsFromRoom(
+	roomNID types.RoomNID,
+) (eventNIDs map[types.EventNID]membershipState, err error) {
+	rows, err := s.selectMembershipsFromRoomStmt.Query(roomNID)
+	if err != nil {
+		return
+	}
+
+	eventNIDs = make(map[types.EventNID]membershipState)
+	for rows.Next() {
+		var eNID types.EventNID
+		var membership membershipState
+		if err = rows.Scan(&membership, &eNID); err != nil {
+			return
+		}
+		eventNIDs[eNID] = membership
+	}
+	return
+}
+func (s *membershipStatements) selectMembershipsFromRoomAndMembership(
+	roomNID types.RoomNID, membership membershipState,
+) (eventNIDs []types.EventNID, err error) {
+	rows, err := s.selectMembershipsFromRoomAndMembershipStmt.Query(roomNID, membership)
+	if err != nil {
+		return
+	}
+
+	for rows.Next() {
+		var eNID types.EventNID
+		if err = rows.Scan(&eNID); err != nil {
+			return
+		}
+		eventNIDs = append(eventNIDs, eNID)
+	}
+	return
+}
+
 func (s *membershipStatements) updateMembership(
 	txn *sql.Tx, roomNID types.RoomNID, targetUserNID types.EventStateKeyNID,
 	senderUserNID types.EventStateKeyNID, membership membershipState,
+	eventNID types.EventNID,
 ) error {
-	_, err := txn.Stmt(s.updateMembershipStmt).Exec(
-		roomNID, targetUserNID, senderUserNID, membership,
+	_, err := common.TxStmt(txn, s.updateMembershipStmt).Exec(
+		roomNID, targetUserNID, senderUserNID, membership, eventNID,
 	)
 	return err
 }
diff --git a/src/github.com/matrix-org/dendrite/roomserver/storage/previous_events_table.go b/src/github.com/matrix-org/dendrite/roomserver/storage/previous_events_table.go
index 71795d488..9fcf1cb5c 100644
--- a/src/github.com/matrix-org/dendrite/roomserver/storage/previous_events_table.go
+++ b/src/github.com/matrix-org/dendrite/roomserver/storage/previous_events_table.go
@@ -17,6 +17,7 @@ package storage
 import (
 	"database/sql"
 
+	"github.com/matrix-org/dendrite/common"
 	"github.com/matrix-org/dendrite/roomserver/types"
 )
 
@@ -73,7 +74,7 @@ func (s *previousEventStatements) prepare(db *sql.DB) (err error) {
 }
 
 func (s *previousEventStatements) insertPreviousEvent(txn *sql.Tx, previousEventID string, previousEventReferenceSHA256 []byte, eventNID types.EventNID) error {
-	_, err := txn.Stmt(s.insertPreviousEventStmt).Exec(previousEventID, previousEventReferenceSHA256, int64(eventNID))
+	_, err := common.TxStmt(txn, s.insertPreviousEventStmt).Exec(previousEventID, previousEventReferenceSHA256, int64(eventNID))
 	return err
 }
 
@@ -81,5 +82,5 @@ func (s *previousEventStatements) insertPreviousEvent(txn *sql.Tx, previousEvent
 // Returns sql.ErrNoRows if the event reference doesn't exist.
 func (s *previousEventStatements) selectPreviousEventExists(txn *sql.Tx, eventID string, eventReferenceSHA256 []byte) error {
 	var ok int64
-	return txn.Stmt(s.selectPreviousEventExistsStmt).QueryRow(eventID, eventReferenceSHA256).Scan(&ok)
+	return common.TxStmt(txn, s.selectPreviousEventExistsStmt).QueryRow(eventID, eventReferenceSHA256).Scan(&ok)
 }
diff --git a/src/github.com/matrix-org/dendrite/roomserver/storage/rooms_table.go b/src/github.com/matrix-org/dendrite/roomserver/storage/rooms_table.go
index 03cacd7db..4ba329f39 100644
--- a/src/github.com/matrix-org/dendrite/roomserver/storage/rooms_table.go
+++ b/src/github.com/matrix-org/dendrite/roomserver/storage/rooms_table.go
@@ -18,6 +18,7 @@ import (
 	"database/sql"
 
 	"github.com/lib/pq"
+	"github.com/matrix-org/dendrite/common"
 	"github.com/matrix-org/dendrite/roomserver/types"
 )
 
@@ -80,15 +81,15 @@ func (s *roomStatements) prepare(db *sql.DB) (err error) {
 	}.prepare(db)
 }
 
-func (s *roomStatements) insertRoomNID(roomID string) (types.RoomNID, error) {
+func (s *roomStatements) insertRoomNID(txn *sql.Tx, roomID string) (types.RoomNID, error) {
 	var roomNID int64
-	err := s.insertRoomNIDStmt.QueryRow(roomID).Scan(&roomNID)
+	err := common.TxStmt(txn, s.insertRoomNIDStmt).QueryRow(roomID).Scan(&roomNID)
 	return types.RoomNID(roomNID), err
 }
 
-func (s *roomStatements) selectRoomNID(roomID string) (types.RoomNID, error) {
+func (s *roomStatements) selectRoomNID(txn *sql.Tx, roomID string) (types.RoomNID, error) {
 	var roomNID int64
-	err := s.selectRoomNIDStmt.QueryRow(roomID).Scan(&roomNID)
+	err := common.TxStmt(txn, s.selectRoomNIDStmt).QueryRow(roomID).Scan(&roomNID)
 	return types.RoomNID(roomNID), err
 }
 
@@ -112,7 +113,7 @@ func (s *roomStatements) selectLatestEventsNIDsForUpdate(txn *sql.Tx, roomNID ty
 	var nids pq.Int64Array
 	var lastEventSentNID int64
 	var stateSnapshotNID int64
-	err := txn.Stmt(s.selectLatestEventNIDsForUpdateStmt).QueryRow(int64(roomNID)).Scan(&nids, &lastEventSentNID, &stateSnapshotNID)
+	err := common.TxStmt(txn, s.selectLatestEventNIDsForUpdateStmt).QueryRow(int64(roomNID)).Scan(&nids, &lastEventSentNID, &stateSnapshotNID)
 	if err != nil {
 		return nil, 0, 0, err
 	}
@@ -127,7 +128,7 @@ func (s *roomStatements) updateLatestEventNIDs(
 	txn *sql.Tx, roomNID types.RoomNID, eventNIDs []types.EventNID, lastEventSentNID types.EventNID,
 	stateSnapshotNID types.StateSnapshotNID,
 ) error {
-	_, err := txn.Stmt(s.updateLatestEventNIDsStmt).Exec(
+	_, err := common.TxStmt(txn, s.updateLatestEventNIDsStmt).Exec(
 		roomNID, eventNIDsAsArray(eventNIDs), int64(lastEventSentNID), int64(stateSnapshotNID),
 	)
 	return err
diff --git a/src/github.com/matrix-org/dendrite/roomserver/storage/storage.go b/src/github.com/matrix-org/dendrite/roomserver/storage/storage.go
index d323fd139..fbbc723ee 100644
--- a/src/github.com/matrix-org/dendrite/roomserver/storage/storage.go
+++ b/src/github.com/matrix-org/dendrite/roomserver/storage/storage.go
@@ -53,7 +53,7 @@ func (d *Database) StoreEvent(event gomatrixserverlib.Event, authEventNIDs []typ
 		err              error
 	)
 
-	if roomNID, err = d.assignRoomNID(event.RoomID()); err != nil {
+	if roomNID, err = d.assignRoomNID(nil, event.RoomID()); err != nil {
 		return 0, types.StateAtEvent{}, err
 	}
 
@@ -104,15 +104,15 @@ func (d *Database) StoreEvent(event gomatrixserverlib.Event, authEventNIDs []typ
 	}, nil
 }
 
-func (d *Database) assignRoomNID(roomID string) (types.RoomNID, error) {
+func (d *Database) assignRoomNID(txn *sql.Tx, roomID string) (types.RoomNID, error) {
 	// Check if we already have a numeric ID in the database.
-	roomNID, err := d.statements.selectRoomNID(roomID)
+	roomNID, err := d.statements.selectRoomNID(txn, roomID)
 	if err == sql.ErrNoRows {
 		// We don't have a numeric ID so insert one into the database.
-		roomNID, err = d.statements.insertRoomNID(roomID)
+		roomNID, err = d.statements.insertRoomNID(txn, roomID)
 		if err == sql.ErrNoRows {
 			// We raced with another insert so run the select again.
-			roomNID, err = d.statements.selectRoomNID(roomID)
+			roomNID, err = d.statements.selectRoomNID(txn, roomID)
 		}
 	}
 	return roomNID, err
@@ -329,7 +329,7 @@ func (u *roomRecentEventsUpdater) MembershipUpdater(targetUserNID types.EventSta
 
 // RoomNID implements query.RoomserverQueryAPIDB
 func (d *Database) RoomNID(roomID string) (types.RoomNID, error) {
-	roomNID, err := d.statements.selectRoomNID(roomID)
+	roomNID, err := d.statements.selectRoomNID(nil, roomID)
 	if err == sql.ErrNoRows {
 		return 0, nil
 	}
@@ -380,6 +380,38 @@ func (d *Database) StateEntriesForTuples(
 	return d.statements.bulkSelectFilteredStateBlockEntries(stateBlockNIDs, stateKeyTuples)
 }
 
+// MembershipUpdater implements input.RoomEventDatabase
+func (d *Database) MembershipUpdater(roomID, targetUserID string) (types.MembershipUpdater, error) {
+	txn, err := d.db.Begin()
+	if err != nil {
+		return nil, err
+	}
+	succeeded := false
+	defer func() {
+		if !succeeded {
+			txn.Rollback()
+		}
+	}()
+
+	roomNID, err := d.assignRoomNID(txn, roomID)
+	if err != nil {
+		return nil, err
+	}
+
+	targetUserNID, err := d.assignStateKeyNID(txn, targetUserID)
+	if err != nil {
+		return nil, err
+	}
+
+	updater, err := d.membershipUpdaterTxn(txn, roomNID, targetUserNID)
+	if err != nil {
+		return nil, err
+	}
+
+	succeeded = true
+	return updater, nil
+}
+
 type membershipUpdater struct {
 	transaction
 	d             *Database
@@ -435,7 +467,7 @@ func (u *membershipUpdater) SetToInvite(event gomatrixserverlib.Event) (bool, er
 	}
 	if u.membership != membershipStateInvite {
 		if err = u.d.statements.updateMembership(
-			u.txn, u.roomNID, u.targetUserNID, senderUserNID, membershipStateInvite,
+			u.txn, u.roomNID, u.targetUserNID, senderUserNID, membershipStateInvite, 0,
 		); err != nil {
 			return false, err
 		}
@@ -444,7 +476,43 @@ func (u *membershipUpdater) SetToInvite(event gomatrixserverlib.Event) (bool, er
 }
 
 // SetToJoin implements types.MembershipUpdater
-func (u *membershipUpdater) SetToJoin(senderUserID string) ([]string, error) {
+func (u *membershipUpdater) SetToJoin(senderUserID string, eventID string, isUpdate bool) ([]string, error) {
+	var inviteEventIDs []string
+
+	senderUserNID, err := u.d.assignStateKeyNID(u.txn, senderUserID)
+	if err != nil {
+		return nil, err
+	}
+
+	// If this is a join event update, there is no invite to update
+	if !isUpdate {
+		inviteEventIDs, err = u.d.statements.updateInviteRetired(
+			u.txn, u.roomNID, u.targetUserNID,
+		)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	// Lookup the NID of the new join event
+	nIDs, err := u.d.EventNIDs([]string{eventID})
+	if err != nil {
+		return nil, err
+	}
+
+	if u.membership != membershipStateJoin || isUpdate {
+		if err = u.d.statements.updateMembership(
+			u.txn, u.roomNID, u.targetUserNID, senderUserNID, membershipStateJoin, nIDs[eventID],
+		); err != nil {
+			return nil, err
+		}
+	}
+
+	return inviteEventIDs, nil
+}
+
+// SetToLeave implements types.MembershipUpdater
+func (u *membershipUpdater) SetToLeave(senderUserID string, eventID string) ([]string, error) {
 	senderUserNID, err := u.d.assignStateKeyNID(u.txn, senderUserID)
 	if err != nil {
 		return nil, err
@@ -455,9 +523,16 @@ func (u *membershipUpdater) SetToJoin(senderUserID string) ([]string, error) {
 	if err != nil {
 		return nil, err
 	}
-	if u.membership != membershipStateJoin {
+
+	// Lookup the NID of the new leave event
+	nIDs, err := u.d.EventNIDs([]string{eventID})
+	if err != nil {
+		return nil, err
+	}
+
+	if u.membership != membershipStateLeaveOrBan {
 		if err = u.d.statements.updateMembership(
-			u.txn, u.roomNID, u.targetUserNID, senderUserNID, membershipStateJoin,
+			u.txn, u.roomNID, u.targetUserNID, senderUserNID, membershipStateLeaveOrBan, nIDs[eventID],
 		); err != nil {
 			return nil, err
 		}
@@ -465,26 +540,49 @@ func (u *membershipUpdater) SetToJoin(senderUserID string) ([]string, error) {
 	return inviteEventIDs, nil
 }
 
-// SetToLeave implements types.MembershipUpdater
-func (u *membershipUpdater) SetToLeave(senderUserID string) ([]string, error) {
-	senderUserNID, err := u.d.assignStateKeyNID(u.txn, senderUserID)
+// GetMembershipEvents implements query.RoomserverQueryAPIDB
+func (d *Database) GetMembershipEvents(roomNID types.RoomNID, requestSenderUserID string) (events []types.Event, err error) {
+	txn, err := d.db.Begin()
 	if err != nil {
-		return nil, err
+		return
 	}
-	inviteEventIDs, err := u.d.statements.updateInviteRetired(
-		u.txn, u.roomNID, u.targetUserNID,
-	)
+	defer txn.Commit()
+
+	requestSenderUserNID, err := d.assignStateKeyNID(txn, requestSenderUserID)
 	if err != nil {
-		return nil, err
+		return
 	}
-	if u.membership != membershipStateLeaveOrBan {
-		if err = u.d.statements.updateMembership(
-			u.txn, u.roomNID, u.targetUserNID, senderUserNID, membershipStateLeaveOrBan,
-		); err != nil {
+
+	_, senderMembership, err := d.statements.selectMembershipFromRoomAndTarget(roomNID, requestSenderUserNID)
+	if err == sql.ErrNoRows {
+		// The user has never been a member of that room
+		return nil, nil
+	} else if err != nil {
+		return
+	}
+
+	if senderMembership == membershipStateJoin {
+		// The user is still in the room: Send the current list of joined members
+		var joinEventNIDs []types.EventNID
+		joinEventNIDs, err = d.statements.selectMembershipsFromRoomAndMembership(roomNID, membershipStateJoin)
+		if err != nil {
 			return nil, err
 		}
+
+		events, err = d.Events(joinEventNIDs)
+	} else {
+		// The user isn't in the room anymore
+		// TODO: Send the list of joined member as it was when the user left
+		//       We cannot do this using only the memberships database, as it
+		//       only stores the latest join event NID for a given target user.
+		//       The solution would be to build the state of a room after before
+		//       the leave event and extract a members list from it.
+		//       For now, we return an empty slice so we know the user has been
+		//       in the room before.
+		events = []types.Event{}
 	}
-	return inviteEventIDs, nil
+
+	return
 }
 
 type transaction struct {
diff --git a/src/github.com/matrix-org/dendrite/roomserver/types/types.go b/src/github.com/matrix-org/dendrite/roomserver/types/types.go
index 809b6e574..d5fe32762 100644
--- a/src/github.com/matrix-org/dendrite/roomserver/types/types.go
+++ b/src/github.com/matrix-org/dendrite/roomserver/types/types.go
@@ -16,6 +16,7 @@
 package types
 
 import (
+	"github.com/matrix-org/dendrite/common"
 	"github.com/matrix-org/gomatrixserverlib"
 )
 
@@ -135,14 +136,6 @@ type StateEntryList struct {
 	StateEntries  []StateEntry
 }
 
-// A Transaction is something that can be committed or rolledback.
-type Transaction interface {
-	// Commit the transaction
-	Commit() error
-	// Rollback the transaction.
-	Rollback() error
-}
-
 // A RoomRecentEventsUpdater is used to update the recent events in a room.
 // (On postgresql this wraps a database transaction that holds a "FOR UPDATE"
 //  lock on the row in the rooms table holding the latest events for the room.)
@@ -175,7 +168,7 @@ type RoomRecentEventsUpdater interface {
 	// It will share the same transaction as this updater.
 	MembershipUpdater(targetUserNID EventStateKeyNID) (MembershipUpdater, error)
 	// Implements Transaction so it can be committed or rolledback
-	Transaction
+	common.Transaction
 }
 
 // A MembershipUpdater is used to update the membership of a user in a room.
@@ -193,14 +186,14 @@ type MembershipUpdater interface {
 	// Set the state to invite.
 	// Returns whether this invite needs to be sent
 	SetToInvite(event gomatrixserverlib.Event) (needsSending bool, err error)
-	// Set the state to join.
+	// Set the state to join or updates the event ID in the database.
 	// Returns a list of invite event IDs that this state change retired.
-	SetToJoin(senderUserID string) (inviteEventIDs []string, err error)
+	SetToJoin(senderUserID string, eventID string, isUpdate bool) (inviteEventIDs []string, err error)
 	// Set the state to leave.
 	// Returns a list of invite event IDs that this state change retired.
-	SetToLeave(senderUserID string) (inviteEventIDs []string, err error)
+	SetToLeave(senderUserID string, eventID string) (inviteEventIDs []string, err error)
 	// Implements Transaction so it can be committed or rolledback.
-	Transaction
+	common.Transaction
 }
 
 // A MissingEventError is an error that happened because the roomserver was
diff --git a/src/github.com/matrix-org/dendrite/syncapi/storage/current_room_state_table.go b/src/github.com/matrix-org/dendrite/syncapi/storage/current_room_state_table.go
index 9958e0d15..10933e965 100644
--- a/src/github.com/matrix-org/dendrite/syncapi/storage/current_room_state_table.go
+++ b/src/github.com/matrix-org/dendrite/syncapi/storage/current_room_state_table.go
@@ -18,6 +18,7 @@ import (
 	"database/sql"
 
 	"github.com/lib/pq"
+	"github.com/matrix-org/dendrite/common"
 	"github.com/matrix-org/gomatrixserverlib"
 )
 
@@ -136,7 +137,7 @@ func (s *currentRoomStateStatements) selectJoinedUsers() (map[string][]string, e
 
 // SelectRoomIDsWithMembership returns the list of room IDs which have the given user in the given membership state.
 func (s *currentRoomStateStatements) selectRoomIDsWithMembership(txn *sql.Tx, userID, membership string) ([]string, error) {
-	rows, err := txn.Stmt(s.selectRoomIDsWithMembershipStmt).Query(userID, membership)
+	rows, err := common.TxStmt(txn, s.selectRoomIDsWithMembershipStmt).Query(userID, membership)
 	if err != nil {
 		return nil, err
 	}
@@ -155,7 +156,7 @@ func (s *currentRoomStateStatements) selectRoomIDsWithMembership(txn *sql.Tx, us
 
 // CurrentState returns all the current state events for the given room.
 func (s *currentRoomStateStatements) selectCurrentState(txn *sql.Tx, roomID string) ([]gomatrixserverlib.Event, error) {
-	rows, err := txn.Stmt(s.selectCurrentStateStmt).Query(roomID)
+	rows, err := common.TxStmt(txn, s.selectCurrentStateStmt).Query(roomID)
 	if err != nil {
 		return nil, err
 	}
@@ -165,21 +166,21 @@ func (s *currentRoomStateStatements) selectCurrentState(txn *sql.Tx, roomID stri
 }
 
 func (s *currentRoomStateStatements) deleteRoomStateByEventID(txn *sql.Tx, eventID string) error {
-	_, err := txn.Stmt(s.deleteRoomStateByEventIDStmt).Exec(eventID)
+	_, err := common.TxStmt(txn, s.deleteRoomStateByEventIDStmt).Exec(eventID)
 	return err
 }
 
 func (s *currentRoomStateStatements) upsertRoomState(
 	txn *sql.Tx, event gomatrixserverlib.Event, membership *string, addedAt int64,
 ) error {
-	_, err := txn.Stmt(s.upsertRoomStateStmt).Exec(
+	_, err := common.TxStmt(txn, s.upsertRoomStateStmt).Exec(
 		event.RoomID(), event.EventID(), event.Type(), *event.StateKey(), event.JSON(), membership, addedAt,
 	)
 	return err
 }
 
 func (s *currentRoomStateStatements) selectEventsWithEventIDs(txn *sql.Tx, eventIDs []string) ([]streamEvent, error) {
-	rows, err := txn.Stmt(s.selectEventsWithEventIDsStmt).Query(pq.StringArray(eventIDs))
+	rows, err := common.TxStmt(txn, s.selectEventsWithEventIDsStmt).Query(pq.StringArray(eventIDs))
 	if err != nil {
 		return nil, err
 	}
diff --git a/src/github.com/matrix-org/dendrite/syncapi/storage/output_room_events_table.go b/src/github.com/matrix-org/dendrite/syncapi/storage/output_room_events_table.go
index f3c46298a..93774d1f1 100644
--- a/src/github.com/matrix-org/dendrite/syncapi/storage/output_room_events_table.go
+++ b/src/github.com/matrix-org/dendrite/syncapi/storage/output_room_events_table.go
@@ -19,6 +19,7 @@ import (
 
 	log "github.com/Sirupsen/logrus"
 	"github.com/lib/pq"
+	"github.com/matrix-org/dendrite/common"
 	"github.com/matrix-org/dendrite/syncapi/types"
 	"github.com/matrix-org/gomatrixserverlib"
 )
@@ -105,7 +106,7 @@ func (s *outputRoomEventsStatements) prepare(db *sql.DB) (err error) {
 func (s *outputRoomEventsStatements) selectStateInRange(
 	txn *sql.Tx, oldPos, newPos types.StreamPosition,
 ) (map[string]map[string]bool, map[string]streamEvent, error) {
-	rows, err := txn.Stmt(s.selectStateInRangeStmt).Query(oldPos, newPos)
+	rows, err := common.TxStmt(txn, s.selectStateInRangeStmt).Query(oldPos, newPos)
 	if err != nil {
 		return nil, nil, err
 	}
@@ -167,12 +168,8 @@ func (s *outputRoomEventsStatements) selectStateInRange(
 // then this function should only ever be used at startup, as it will race with inserting events if it is
 // done afterwards. If there are no inserted events, 0 is returned.
 func (s *outputRoomEventsStatements) selectMaxID(txn *sql.Tx) (id int64, err error) {
-	stmt := s.selectMaxIDStmt
-	if txn != nil {
-		stmt = txn.Stmt(stmt)
-	}
 	var nullableID sql.NullInt64
-	err = stmt.QueryRow().Scan(&nullableID)
+	err = common.TxStmt(txn, s.selectMaxIDStmt).QueryRow().Scan(&nullableID)
 	if nullableID.Valid {
 		id = nullableID.Int64
 	}
@@ -182,7 +179,7 @@ func (s *outputRoomEventsStatements) selectMaxID(txn *sql.Tx) (id int64, err err
 // InsertEvent into the output_room_events table. addState and removeState are an optional list of state event IDs. Returns the position
 // of the inserted event.
 func (s *outputRoomEventsStatements) insertEvent(txn *sql.Tx, event *gomatrixserverlib.Event, addState, removeState []string) (streamPos int64, err error) {
-	err = txn.Stmt(s.insertEventStmt).QueryRow(
+	err = common.TxStmt(txn, s.insertEventStmt).QueryRow(
 		event.RoomID(), event.EventID(), event.JSON(), pq.StringArray(addState), pq.StringArray(removeState),
 	).Scan(&streamPos)
 	return
@@ -209,11 +206,7 @@ func (s *outputRoomEventsStatements) selectRecentEvents(
 // Events returns the events for the given event IDs. Returns an error if any one of the event IDs given are missing
 // from the database.
 func (s *outputRoomEventsStatements) selectEvents(txn *sql.Tx, eventIDs []string) ([]streamEvent, error) {
-	stmt := s.selectEventsStmt
-	if txn != nil {
-		stmt = txn.Stmt(stmt)
-	}
-	rows, err := stmt.Query(pq.StringArray(eventIDs))
+	rows, err := common.TxStmt(txn, s.selectEventsStmt).Query(pq.StringArray(eventIDs))
 	if err != nil {
 		return nil, err
 	}