diff --git a/CHANGES.md b/CHANGES.md
index 3df03b2f6..0ae927446 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,5 +1,35 @@
 # Changelog
 
+## Dendrite 0.9.0 (2022-08-01)
+
+### Features
+
+* Dendrite now uses Ristretto for managing in-memory caches
+  * Should improve cache utilisation considerably over time by more intelligently selecting and managing cache entries compared to the previous LRU-based cache
+  * Defaults to a 1GB cache size if not configured otherwise
+  * The estimated cache size in memory and maximum age can now be configured with new [configuration options](https://github.com/matrix-org/dendrite/blob/e94ef84aaba30e12baf7f524c4e7a36d2fdeb189/dendrite-sample.monolith.yaml#L44-L61) to prevent unbounded cache growth
+* Added support for serving the `/.well-known/matrix/client` hint directly from Dendrite
+  * Configurable with the new [configuration option](https://github.com/matrix-org/dendrite/blob/e94ef84aaba30e12baf7f524c4e7a36d2fdeb189/dendrite-sample.monolith.yaml#L67-L69)
+* Refactored membership updater, which should eliminate some bugs caused by the membership table getting out of sync with the room state
+* The User API is now responsible for sending account data updates to other components, which may fix some races and duplicate account data events
+* Optimised database query for checking whether a remote server is allowed to request an event over federation without using anywhere near as much CPU time (PostgreSQL only)
+* Database migrations have been refactored to eliminate some problems that were present with `goose` and upgrading from older Dendrite versions
+* Media fetching will now use the `/v3` endpoints for downloading media from remote homeservers
+* HTTP 404 and HTTP 405 errors from the client-facing APIs should now be returned with CORS headers so that web-based clients do not produce incorrect access control warnings for unknown endpoints
+* Some preparation work for full history visibility support
+
+### Fixes
+
+* Fixes a crash that could occur during event redaction
+* The `/members` endpoint will no longer incorrectly return HTTP 500 as a result of some invite events
+* Send-to-device messages should now be ordered more reliably and the last position in the stream updated correctly
+* Parsing of appservice configuration files is now less strict (contributed by [Kab1r](https://github.com/Kab1r))
+* The sync API should now identify shared users correctly when waking up for E2EE key changes
+* The federation `/state` endpoint will now return a HTTP 403 when the state before an event isn't known instead of a HTTP 500
+* Presence timestamps should now be calculated with the correct precision
+* A race condition in the roomserver's room info has been fixed
+* A race condition in the sync API has been fixed
+
 ## Dendrite 0.8.9 (2022-07-01)
 
 ### Features
diff --git a/dendrite-sample.monolith.yaml b/dendrite-sample.monolith.yaml
index cc6c173e8..a34b8af55 100644
--- a/dendrite-sample.monolith.yaml
+++ b/dendrite-sample.monolith.yaml
@@ -113,6 +113,11 @@ global:
     addresses:
     # - localhost:4222
 
+    # Disable the validation of TLS certificates of NATS. This is
+    # not recommended in production since it may allow NATS traffic
+    # to be sent to an insecure endpoint.
+    disable_tls_validation: false
+
     # Persistent directory to store JetStream streams in. This directory should be
     # preserved across Dendrite restarts.
     storage_path: ./
diff --git a/dendrite-sample.polylith.yaml b/dendrite-sample.polylith.yaml
index 92cab19b1..550611229 100644
--- a/dendrite-sample.polylith.yaml
+++ b/dendrite-sample.polylith.yaml
@@ -103,6 +103,11 @@ global:
     addresses:
       - hostname:4222
 
+    # Disable the validation of TLS certificates of NATS. This is
+    # not recommended in production since it may allow NATS traffic
+    # to be sent to an insecure endpoint.
+    disable_tls_validation: false
+
     # The prefix to use for stream names for this homeserver - really only useful
     # if you are running more than one Dendrite server on the same NATS deployment.
     topic_prefix: Dendrite
diff --git a/federationapi/routing/join.go b/federationapi/routing/join.go
index 41004cf51..30406a155 100644
--- a/federationapi/routing/join.go
+++ b/federationapi/routing/join.go
@@ -202,6 +202,14 @@ func SendJoin(
 		}
 	}
 
+	// Check that the event is from the server sending the request.
+	if event.Origin() != request.Origin() {
+		return util.JSONResponse{
+			Code: http.StatusForbidden,
+			JSON: jsonerror.Forbidden("The join must be sent by the server it originated on"),
+		}
+	}
+
 	// Check that a state key is provided.
 	if event.StateKey() == nil || event.StateKeyEquals("") {
 		return util.JSONResponse{
@@ -216,6 +224,22 @@ func SendJoin(
 		}
 	}
 
+	// Check that the sender belongs to the server that is sending us
+	// the request. By this point we've already asserted that the sender
+	// and the state key are equal so we don't need to check both.
+	var domain gomatrixserverlib.ServerName
+	if _, domain, err = gomatrixserverlib.SplitID('@', event.Sender()); err != nil {
+		return util.JSONResponse{
+			Code: http.StatusForbidden,
+			JSON: jsonerror.Forbidden("The sender of the join is invalid"),
+		}
+	} else if domain != request.Origin() {
+		return util.JSONResponse{
+			Code: http.StatusForbidden,
+			JSON: jsonerror.Forbidden("The sender of the join must belong to the origin server"),
+		}
+	}
+
 	// Check that the room ID is correct.
 	if event.RoomID() != roomID {
 		return util.JSONResponse{
@@ -242,14 +266,6 @@ func SendJoin(
 		}
 	}
 
-	// Check that the event is from the server sending the request.
-	if event.Origin() != request.Origin() {
-		return util.JSONResponse{
-			Code: http.StatusForbidden,
-			JSON: jsonerror.Forbidden("The join must be sent by the server it originated on"),
-		}
-	}
-
 	// Check that this is in fact a join event
 	membership, err := event.Membership()
 	if err != nil {
diff --git a/go.mod b/go.mod
index 377a156fe..5b2d8670d 100644
--- a/go.mod
+++ b/go.mod
@@ -1,9 +1,5 @@
 module github.com/matrix-org/dendrite
 
-replace github.com/nats-io/nats-server/v2 => github.com/neilalexander/nats-server/v2 v2.8.3-0.20220513095553-73a9a246d34f
-
-replace github.com/nats-io/nats.go => github.com/neilalexander/nats.go v1.13.1-0.20220621084451-ac518c356673
-
 require (
 	github.com/Arceliar/ironwood v0.0.0-20220306165321-319147a02d98
 	github.com/Arceliar/phony v0.0.0-20210209235338-dde1a8dca979
@@ -29,8 +25,8 @@ require (
 	github.com/matrix-org/pinecone v0.0.0-20220708135211-1ce778fcde6a
 	github.com/matrix-org/util v0.0.0-20200807132607-55161520e1d4
 	github.com/mattn/go-sqlite3 v1.14.13
-	github.com/nats-io/nats-server/v2 v2.7.4-0.20220309205833-773636c1c5bb
-	github.com/nats-io/nats.go v1.14.0
+	github.com/nats-io/nats-server/v2 v2.8.5-0.20220731184415-903a06a5b4ee
+	github.com/nats-io/nats.go v1.16.1-0.20220731182438-87bbea85922b
 	github.com/neilalexander/utp v0.1.1-0.20210727203401-54ae7b1cd5f9
 	github.com/nfnt/resize v0.0.0-20180221191011-83c6a9932646
 	github.com/ngrok/sqlmw v0.0.0-20220520173518-97c9c04efc79
@@ -76,7 +72,7 @@ require (
 	github.com/h2non/filetype v1.1.3 // indirect
 	github.com/juju/errors v0.0.0-20220203013757-bd733f3c86b9 // indirect
 	github.com/juju/testing v0.0.0-20220203020004-a0ff61f03494 // indirect
-	github.com/klauspost/compress v1.14.4 // indirect
+	github.com/klauspost/compress v1.15.9 // indirect
 	github.com/lucas-clemente/quic-go v0.26.0 // indirect
 	github.com/marten-seemann/qtls-go1-16 v0.1.5 // indirect
 	github.com/marten-seemann/qtls-go1-17 v0.1.1 // indirect
@@ -86,7 +82,7 @@ require (
 	github.com/minio/highwayhash v1.0.2 // indirect
 	github.com/moby/term v0.0.0-20210610120745-9d4ed1856297 // indirect
 	github.com/morikuni/aec v1.0.0 // indirect
-	github.com/nats-io/jwt/v2 v2.2.1-0.20220330180145-442af02fd36a // indirect
+	github.com/nats-io/jwt/v2 v2.3.0 // indirect
 	github.com/nats-io/nkeys v0.3.0 // indirect
 	github.com/nats-io/nuid v1.0.1 // indirect
 	github.com/nxadm/tail v1.4.8 // indirect
@@ -104,7 +100,7 @@ require (
 	golang.org/x/mod v0.6.0-dev.0.20220106191415-9b9b3d81d5e3 // indirect
 	golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a // indirect
 	golang.org/x/text v0.3.8-0.20211004125949-5bd84dd9b33b // indirect
-	golang.org/x/time v0.0.0-20211116232009-f0f3c7e86c11 // indirect
+	golang.org/x/time v0.0.0-20220411224347-583f2d630306 // indirect
 	golang.org/x/tools v0.1.10 // indirect
 	golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 // indirect
 	google.golang.org/protobuf v1.27.1 // indirect
diff --git a/go.sum b/go.sum
index 10b1638a5..6321adada 100644
--- a/go.sum
+++ b/go.sum
@@ -302,8 +302,8 @@ github.com/kardianos/minwinsvc v1.0.0/go.mod h1:Bgd0oc+D0Qo3bBytmNtyRKVlp85dAloL
 github.com/kisielk/errcheck v1.5.0/go.mod h1:pFxgyoBC7bSaBwPgfKdkLd5X25qrDl4LWUI2bnpBCr8=
 github.com/kisielk/gotool v1.0.0/go.mod h1:XhKaO+MFFWcvkIS/tQcRk01m1F5IRFswLeQ+oQHNcck=
 github.com/klauspost/compress v1.10.3/go.mod h1:aoV0uJVorq1K+umq18yTdKaF57EivdYsUV+/s2qKfXs=
-github.com/klauspost/compress v1.14.4 h1:eijASRJcobkVtSt81Olfh7JX43osYLwy5krOJo6YEu4=
-github.com/klauspost/compress v1.14.4/go.mod h1:/3/Vjq9QcHkK5uEr5lBEmyoZ1iFhe47etQ6QUkpK6sk=
+github.com/klauspost/compress v1.15.9 h1:wKRjX6JRtDdrE9qwa4b/Cip7ACOshUI4smpCQanqjSY=
+github.com/klauspost/compress v1.15.9/go.mod h1:PhcZ0MbTNciWF3rruxRgKxI5NkcHHrHUDtV4Yw2GlzU=
 github.com/konsorten/go-windows-terminal-sequences v1.0.1/go.mod h1:T0+1ngSBFLxvqU3pZ+m/2kptfBszLMUkC4ZK/EgS/cQ=
 github.com/konsorten/go-windows-terminal-sequences v1.0.2/go.mod h1:T0+1ngSBFLxvqU3pZ+m/2kptfBszLMUkC4ZK/EgS/cQ=
 github.com/konsorten/go-windows-terminal-sequences v1.0.3/go.mod h1:T0+1ngSBFLxvqU3pZ+m/2kptfBszLMUkC4ZK/EgS/cQ=
@@ -381,8 +381,12 @@ github.com/morikuni/aec v1.0.0/go.mod h1:BbKIizmSmc5MMPqRYbxO4ZU0S0+P200+tUnFx7P
 github.com/mschoch/smat v0.0.0-20160514031455-90eadee771ae/go.mod h1:qAyveg+e4CE+eKJXWVjKXM4ck2QobLqTDytGJbLLhJg=
 github.com/mwitkow/go-conntrack v0.0.0-20161129095857-cc309e4a2223/go.mod h1:qRWi+5nqEBWmkhHvq77mSJWrCKwh8bxhgT7d/eI7P4U=
 github.com/mwitkow/go-conntrack v0.0.0-20190716064945-2f068394615f/go.mod h1:qRWi+5nqEBWmkhHvq77mSJWrCKwh8bxhgT7d/eI7P4U=
-github.com/nats-io/jwt/v2 v2.2.1-0.20220330180145-442af02fd36a h1:lem6QCvxR0Y28gth9P+wV2K/zYUUAkJ+55U8cpS0p5I=
-github.com/nats-io/jwt/v2 v2.2.1-0.20220330180145-442af02fd36a/go.mod h1:0tqz9Hlu6bCBFLWAASKhE5vUA4c24L9KPUUgvwumE/k=
+github.com/nats-io/jwt/v2 v2.3.0 h1:z2mA1a7tIf5ShggOFlR1oBPgd6hGqcDYsISxZByUzdI=
+github.com/nats-io/jwt/v2 v2.3.0/go.mod h1:0tqz9Hlu6bCBFLWAASKhE5vUA4c24L9KPUUgvwumE/k=
+github.com/nats-io/nats-server/v2 v2.8.5-0.20220731184415-903a06a5b4ee h1:vAtoZ+LW6eIUjkCWWwO1DZ6o16UGrVOG+ot/AkwejO8=
+github.com/nats-io/nats-server/v2 v2.8.5-0.20220731184415-903a06a5b4ee/go.mod h1:3Yg3ApyQxPlAs1KKHKV5pobV5VtZk+TtOiUJx/iqkkg=
+github.com/nats-io/nats.go v1.16.1-0.20220731182438-87bbea85922b h1:CE9wSYLvwq8aC/0+6zH8lhhtZYvJ9p8PzwvZeYgdBc0=
+github.com/nats-io/nats.go v1.16.1-0.20220731182438-87bbea85922b/go.mod h1:BPko4oXsySz4aSWeFgOHLZs3G4Jq4ZAyE6/zMCxRT6w=
 github.com/nats-io/nkeys v0.3.0 h1:cgM5tL53EvYRU+2YLXIK0G2mJtK12Ft9oeooSZMA2G8=
 github.com/nats-io/nkeys v0.3.0/go.mod h1:gvUNGjVcM2IPr5rCsRsC6Wb3Hr2CQAm08dsxtV6A5y4=
 github.com/nats-io/nuid v1.0.1 h1:5iA8DT8V7q8WK2EScv2padNa/rTESc1KdnPw4TC2paw=
@@ -390,10 +394,6 @@ github.com/nats-io/nuid v1.0.1/go.mod h1:19wcPz3Ph3q0Jbyiqsd0kePYG7A95tJPxeL+1OS
 github.com/nbio/st v0.0.0-20140626010706-e9e8d9816f32/go.mod h1:9wM+0iRr9ahx58uYLpLIr5fm8diHn0JbqRycJi6w0Ms=
 github.com/neelance/astrewrite v0.0.0-20160511093645-99348263ae86/go.mod h1:kHJEU3ofeGjhHklVoIGuVj85JJwZ6kWPaJwCIxgnFmo=
 github.com/neelance/sourcemap v0.0.0-20151028013722-8c68805598ab/go.mod h1:Qr6/a/Q4r9LP1IltGz7tA7iOK1WonHEYhu1HRBA7ZiM=
-github.com/neilalexander/nats-server/v2 v2.8.3-0.20220513095553-73a9a246d34f h1:Fc+TjdV1mOy0oISSzfoxNWdTqjg7tN/Vdgf+B2cwvdo=
-github.com/neilalexander/nats-server/v2 v2.8.3-0.20220513095553-73a9a246d34f/go.mod h1:vIdpKz3OG+DCg4q/xVPdXHoztEyKDWRtykQ4N7hd7C4=
-github.com/neilalexander/nats.go v1.13.1-0.20220621084451-ac518c356673 h1:TcKfa3Tf0qwUotv63PQVu2d1bBoLi2iEA4RHVMGDh5M=
-github.com/neilalexander/nats.go v1.13.1-0.20220621084451-ac518c356673/go.mod h1:BPko4oXsySz4aSWeFgOHLZs3G4Jq4ZAyE6/zMCxRT6w=
 github.com/neilalexander/utp v0.1.1-0.20210727203401-54ae7b1cd5f9 h1:lrVQzBtkeQEGGYUHwSX1XPe1E5GL6U3KYCNe2G4bncQ=
 github.com/neilalexander/utp v0.1.1-0.20210727203401-54ae7b1cd5f9/go.mod h1:NPHGhPc0/wudcaCqL/H5AOddkRf8GPRhzOujuUKGQu8=
 github.com/nfnt/resize v0.0.0-20180221191011-83c6a9932646 h1:zYyBkD/k9seD2A7fsi6Oo2LfFZAehjjQMERAvZLEDnQ=
@@ -764,8 +764,8 @@ golang.org/x/time v0.0.0-20180412165947-fbb02b2291d2/go.mod h1:tRJNPiyCQ0inRvYxb
 golang.org/x/time v0.0.0-20181108054448-85acf8d2951c/go.mod h1:tRJNPiyCQ0inRvYxbN9jk5I+vvW/OXSQhTDSoE431IQ=
 golang.org/x/time v0.0.0-20190308202827-9d24e82272b4/go.mod h1:tRJNPiyCQ0inRvYxbN9jk5I+vvW/OXSQhTDSoE431IQ=
 golang.org/x/time v0.0.0-20191024005414-555d28b269f0/go.mod h1:tRJNPiyCQ0inRvYxbN9jk5I+vvW/OXSQhTDSoE431IQ=
-golang.org/x/time v0.0.0-20211116232009-f0f3c7e86c11 h1:GZokNIeuVkl3aZHJchRrr13WCsols02MLUcz1U9is6M=
-golang.org/x/time v0.0.0-20211116232009-f0f3c7e86c11/go.mod h1:tRJNPiyCQ0inRvYxbN9jk5I+vvW/OXSQhTDSoE431IQ=
+golang.org/x/time v0.0.0-20220411224347-583f2d630306 h1:+gHMid33q6pen7kv9xvT+JRinntgeXO2AeZVd0AWD3w=
+golang.org/x/time v0.0.0-20220411224347-583f2d630306/go.mod h1:tRJNPiyCQ0inRvYxbN9jk5I+vvW/OXSQhTDSoE431IQ=
 golang.org/x/tools v0.0.0-20180525024113-a5b4c53f6e8b/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 golang.org/x/tools v0.0.0-20180828015842-6cd1fcedba52/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
diff --git a/internal/sqlutil/migrate.go b/internal/sqlutil/migrate.go
index cb0aed7d3..56d906f29 100644
--- a/internal/sqlutil/migrate.go
+++ b/internal/sqlutil/migrate.go
@@ -48,9 +48,11 @@ type Migration struct {
 	Down func(ctx context.Context, txn *sql.Tx) error
 }
 
+// Gaurs the internal state of Goose from being modified by concurrent tests or goroutines
+var gooseMutex sync.Mutex
+
 // Migrator
 type Migrator struct {
-	gooseMutex      sync.Mutex
 	db              *sql.DB
 	migrations      []Migration
 	knownMigrations map[string]struct{}
@@ -82,8 +84,8 @@ func (m *Migrator) AddMigrations(migrations ...Migration) {
 
 // Up executes all migrations in order they were added.
 func (m *Migrator) Up(ctx context.Context) error {
-	m.gooseMutex.Lock()
-	defer m.gooseMutex.Unlock()
+	gooseMutex.Lock()
+	defer gooseMutex.Unlock()
 	var (
 		err             error
 		dendriteVersion = internal.VersionString()
diff --git a/internal/version.go b/internal/version.go
index 9568f08cb..6d29a68ee 100644
--- a/internal/version.go
+++ b/internal/version.go
@@ -16,8 +16,8 @@ var build string
 
 const (
 	VersionMajor = 0
-	VersionMinor = 8
-	VersionPatch = 9
+	VersionMinor = 9
+	VersionPatch = 0
 	VersionTag   = "" // example: "rc1"
 )
 
diff --git a/roomserver/internal/helpers/auth.go b/roomserver/internal/helpers/auth.go
index 0229f822f..648c50cf6 100644
--- a/roomserver/internal/helpers/auth.go
+++ b/roomserver/internal/helpers/auth.go
@@ -50,14 +50,14 @@ func CheckForSoftFail(
 		if err != nil {
 			return false, fmt.Errorf("db.RoomNID: %w", err)
 		}
-		if roomInfo == nil || roomInfo.IsStub {
+		if roomInfo == nil || roomInfo.IsStub() {
 			return false, nil
 		}
 
 		// Then get the state entries for the current state snapshot.
 		// We'll use this to check if the event is allowed right now.
 		roomState := state.NewStateResolution(db, roomInfo)
-		authStateEntries, err = roomState.LoadStateAtSnapshot(ctx, roomInfo.StateSnapshotNID)
+		authStateEntries, err = roomState.LoadStateAtSnapshot(ctx, roomInfo.StateSnapshotNID())
 		if err != nil {
 			return true, fmt.Errorf("roomState.LoadStateAtSnapshot: %w", err)
 		}
diff --git a/roomserver/internal/helpers/helpers.go b/roomserver/internal/helpers/helpers.go
index 2653027e9..d61aa08cb 100644
--- a/roomserver/internal/helpers/helpers.go
+++ b/roomserver/internal/helpers/helpers.go
@@ -236,13 +236,34 @@ func LoadStateEvents(
 func CheckServerAllowedToSeeEvent(
 	ctx context.Context, db storage.Database, info *types.RoomInfo, eventID string, serverName gomatrixserverlib.ServerName, isServerInRoom bool,
 ) (bool, error) {
+	stateAtEvent, err := db.GetHistoryVisibilityState(ctx, info, eventID, string(serverName))
+	switch err {
+	case nil:
+		// No error, so continue normally
+	case tables.OptimisationNotSupportedError:
+		// The database engine didn't support this optimisation, so fall back to using
+		// the old and slow method
+		stateAtEvent, err = slowGetHistoryVisibilityState(ctx, db, info, eventID, serverName)
+		if err != nil {
+			return false, err
+		}
+	default:
+		// Something else went wrong
+		return false, err
+	}
+	return auth.IsServerAllowed(serverName, isServerInRoom, stateAtEvent), nil
+}
+
+func slowGetHistoryVisibilityState(
+	ctx context.Context, db storage.Database, info *types.RoomInfo, eventID string, serverName gomatrixserverlib.ServerName,
+) ([]*gomatrixserverlib.Event, error) {
 	roomState := state.NewStateResolution(db, info)
 	stateEntries, err := roomState.LoadStateAtEvent(ctx, eventID)
 	if err != nil {
 		if errors.Is(err, sql.ErrNoRows) {
-			return false, nil
+			return nil, nil
 		}
-		return false, fmt.Errorf("roomState.LoadStateAtEvent: %w", err)
+		return nil, fmt.Errorf("roomState.LoadStateAtEvent: %w", err)
 	}
 
 	// Extract all of the event state key NIDs from the room state.
@@ -254,7 +275,7 @@ func CheckServerAllowedToSeeEvent(
 	// Then request those state key NIDs from the database.
 	stateKeys, err := db.EventStateKeys(ctx, stateKeyNIDs)
 	if err != nil {
-		return false, fmt.Errorf("db.EventStateKeys: %w", err)
+		return nil, fmt.Errorf("db.EventStateKeys: %w", err)
 	}
 
 	// If the event state key doesn't match the given servername
@@ -277,15 +298,10 @@ func CheckServerAllowedToSeeEvent(
 	}
 
 	if len(filteredEntries) == 0 {
-		return false, nil
+		return nil, nil
 	}
 
-	stateAtEvent, err := LoadStateEvents(ctx, db, filteredEntries)
-	if err != nil {
-		return false, err
-	}
-
-	return auth.IsServerAllowed(serverName, isServerInRoom, stateAtEvent), nil
+	return LoadStateEvents(ctx, db, filteredEntries)
 }
 
 // TODO: Remove this when we have tests to assert correctness of this function
@@ -393,7 +409,7 @@ func QueryLatestEventsAndState(
 	if err != nil {
 		return err
 	}
-	if roomInfo == nil || roomInfo.IsStub {
+	if roomInfo == nil || roomInfo.IsStub() {
 		response.RoomExists = false
 		return nil
 	}
diff --git a/roomserver/internal/input/input_missing.go b/roomserver/internal/input/input_missing.go
index edc153b7f..c78e5d79a 100644
--- a/roomserver/internal/input/input_missing.go
+++ b/roomserver/internal/input/input_missing.go
@@ -375,11 +375,7 @@ func (t *missingStateReq) lookupStateAfterEventLocally(ctx context.Context, room
 	defer span.Finish()
 
 	var res parsedRespState
-	roomInfo, err := t.db.RoomInfo(ctx, roomID)
-	if err != nil {
-		return nil
-	}
-	roomState := state.NewStateResolution(t.db, roomInfo)
+	roomState := state.NewStateResolution(t.db, t.roomInfo)
 	stateAtEvents, err := t.db.StateAtEventIDs(ctx, []string{eventID})
 	if err != nil {
 		util.GetLogger(ctx).WithField("room_id", roomID).WithError(err).Warnf("failed to get state after %s locally", eventID)
@@ -754,9 +750,8 @@ func (t *missingStateReq) lookupMissingStateViaStateIDs(ctx context.Context, roo
 
 		// Define what we'll do in order to fetch the missing event ID.
 		fetch := func(missingEventID string) {
-			var h *gomatrixserverlib.Event
-			h, err = t.lookupEvent(ctx, roomVersion, roomID, missingEventID, false)
-			switch err.(type) {
+			h, herr := t.lookupEvent(ctx, roomVersion, roomID, missingEventID, false)
+			switch herr.(type) {
 			case verifySigError:
 				return
 			case nil:
@@ -765,7 +760,7 @@ func (t *missingStateReq) lookupMissingStateViaStateIDs(ctx context.Context, roo
 				util.GetLogger(ctx).WithFields(logrus.Fields{
 					"event_id": missingEventID,
 					"room_id":  roomID,
-				}).Warn("Failed to fetch missing event")
+				}).WithError(herr).Warn("Failed to fetch missing event")
 				return
 			}
 			haveEventsMutex.Lock()
diff --git a/roomserver/internal/perform/perform_admin.go b/roomserver/internal/perform/perform_admin.go
index 1cb52966a..6c7c6c98b 100644
--- a/roomserver/internal/perform/perform_admin.go
+++ b/roomserver/internal/perform/perform_admin.go
@@ -52,7 +52,7 @@ func (r *Admin) PerformAdminEvacuateRoom(
 		}
 		return
 	}
-	if roomInfo == nil || roomInfo.IsStub {
+	if roomInfo == nil || roomInfo.IsStub() {
 		res.Error = &api.PerformError{
 			Code: api.PerformErrorNoRoom,
 			Msg:  fmt.Sprintf("Room %s not found", req.RoomID),
diff --git a/roomserver/internal/perform/perform_backfill.go b/roomserver/internal/perform/perform_backfill.go
index 3f98fbc24..5b7ed22ee 100644
--- a/roomserver/internal/perform/perform_backfill.go
+++ b/roomserver/internal/perform/perform_backfill.go
@@ -73,7 +73,7 @@ func (r *Backfiller) PerformBackfill(
 	if err != nil {
 		return err
 	}
-	if info == nil || info.IsStub {
+	if info == nil || info.IsStub() {
 		return fmt.Errorf("PerformBackfill: missing room info for room %s", request.RoomID)
 	}
 
@@ -106,7 +106,7 @@ func (r *Backfiller) backfillViaFederation(ctx context.Context, req *api.Perform
 	if err != nil {
 		return err
 	}
-	if info == nil || info.IsStub {
+	if info == nil || info.IsStub() {
 		return fmt.Errorf("backfillViaFederation: missing room info for room %s", req.RoomID)
 	}
 	requester := newBackfillRequester(r.DB, r.FSAPI, r.ServerName, req.BackwardsExtremities, r.PreferServers)
@@ -434,7 +434,7 @@ FindSuccessor:
 		logrus.WithError(err).WithField("room_id", roomID).Error("ServersAtEvent: failed to get RoomInfo for room")
 		return nil
 	}
-	if info == nil || info.IsStub {
+	if info == nil || info.IsStub() {
 		logrus.WithField("room_id", roomID).Error("ServersAtEvent: failed to get RoomInfo for room, room is missing")
 		return nil
 	}
diff --git a/roomserver/internal/perform/perform_inbound_peek.go b/roomserver/internal/perform/perform_inbound_peek.go
index 32c81e849..29decd363 100644
--- a/roomserver/internal/perform/perform_inbound_peek.go
+++ b/roomserver/internal/perform/perform_inbound_peek.go
@@ -50,7 +50,7 @@ func (r *InboundPeeker) PerformInboundPeek(
 	if err != nil {
 		return err
 	}
-	if info == nil || info.IsStub {
+	if info == nil || info.IsStub() {
 		return nil
 	}
 	response.RoomExists = true
diff --git a/roomserver/internal/perform/perform_invite.go b/roomserver/internal/perform/perform_invite.go
index fce529305..e1ff4eabb 100644
--- a/roomserver/internal/perform/perform_invite.go
+++ b/roomserver/internal/perform/perform_invite.go
@@ -125,7 +125,7 @@ func (r *Inviter) PerformInvite(
 		return outputUpdates, nil
 	}
 
-	if (info == nil || info.IsStub) && !isOriginLocal && isTargetLocal {
+	if (info == nil || info.IsStub()) && !isOriginLocal && isTargetLocal {
 		// The invite came in over federation for a room that we don't know about
 		// yet. We need to handle this a bit differently to most invites because
 		// we don't know the room state, therefore the roomserver can't process
@@ -276,7 +276,7 @@ func buildInviteStrippedState(
 	}
 	roomState := state.NewStateResolution(db, info)
 	stateEntries, err := roomState.LoadStateAtSnapshotForStringTuples(
-		ctx, info.StateSnapshotNID, stateWanted,
+		ctx, info.StateSnapshotNID(), stateWanted,
 	)
 	if err != nil {
 		return nil, err
diff --git a/roomserver/internal/query/query.go b/roomserver/internal/query/query.go
index f652a8ea3..5ba59b8f5 100644
--- a/roomserver/internal/query/query.go
+++ b/roomserver/internal/query/query.go
@@ -61,7 +61,7 @@ func (r *Queryer) QueryStateAfterEvents(
 	if err != nil {
 		return err
 	}
-	if info == nil || info.IsStub {
+	if info == nil || info.IsStub() {
 		return nil
 	}
 
@@ -302,7 +302,7 @@ func (r *Queryer) QueryServerJoinedToRoom(
 	if err != nil {
 		return fmt.Errorf("r.DB.RoomInfo: %w", err)
 	}
-	if info == nil || info.IsStub {
+	if info == nil || info.IsStub() {
 		return nil
 	}
 	response.RoomExists = true
@@ -351,8 +351,8 @@ func (r *Queryer) QueryServerAllowedToSeeEvent(
 	if err != nil {
 		return err
 	}
-	if info == nil {
-		return fmt.Errorf("QueryServerAllowedToSeeEvent: no room info for room %s", roomID)
+	if info == nil || info.IsStub() {
+		return nil
 	}
 	response.AllowedToSeeEvent, err = helpers.CheckServerAllowedToSeeEvent(
 		ctx, r.DB, info, request.EventID, request.ServerName, inRoomRes.IsInRoom,
@@ -390,7 +390,7 @@ func (r *Queryer) QueryMissingEvents(
 	if err != nil {
 		return err
 	}
-	if info == nil || info.IsStub {
+	if info == nil || info.IsStub() {
 		return fmt.Errorf("missing RoomInfo for room %s", events[0].RoomID())
 	}
 
@@ -429,7 +429,7 @@ func (r *Queryer) QueryStateAndAuthChain(
 	if err != nil {
 		return err
 	}
-	if info == nil || info.IsStub {
+	if info == nil || info.IsStub() {
 		return nil
 	}
 	response.RoomExists = true
@@ -774,7 +774,7 @@ func (r *Queryer) QueryRestrictedJoinAllowed(ctx context.Context, req *api.Query
 	if err != nil {
 		return fmt.Errorf("r.DB.RoomInfo: %w", err)
 	}
-	if roomInfo == nil || roomInfo.IsStub {
+	if roomInfo == nil || roomInfo.IsStub() {
 		return nil // fmt.Errorf("room %q doesn't exist or is stub room", req.RoomID)
 	}
 	// If the room version doesn't allow restricted joins then don't
@@ -837,7 +837,7 @@ func (r *Queryer) QueryRestrictedJoinAllowed(ctx context.Context, req *api.Query
 		// See if the room exists. If it doesn't exist or if it's a stub
 		// room entry then we can't check memberships.
 		targetRoomInfo, err := r.DB.RoomInfo(ctx, rule.RoomID)
-		if err != nil || targetRoomInfo == nil || targetRoomInfo.IsStub {
+		if err != nil || targetRoomInfo == nil || targetRoomInfo.IsStub() {
 			res.Resident = false
 			continue
 		}
diff --git a/roomserver/state/state.go b/roomserver/state/state.go
index d1d24b099..ca0c69f27 100644
--- a/roomserver/state/state.go
+++ b/roomserver/state/state.go
@@ -124,6 +124,29 @@ func (v *StateResolution) LoadStateAtEvent(
 	return stateEntries, nil
 }
 
+// LoadStateAtEvent loads the full state of a room before a particular event.
+func (v *StateResolution) LoadStateAtEventForHistoryVisibility(
+	ctx context.Context, eventID string,
+) ([]types.StateEntry, error) {
+	span, ctx := opentracing.StartSpanFromContext(ctx, "StateResolution.LoadStateAtEvent")
+	defer span.Finish()
+
+	snapshotNID, err := v.db.SnapshotNIDFromEventID(ctx, eventID)
+	if err != nil {
+		return nil, fmt.Errorf("LoadStateAtEvent.SnapshotNIDFromEventID failed for event %s : %w", eventID, err)
+	}
+	if snapshotNID == 0 {
+		return nil, fmt.Errorf("LoadStateAtEvent.SnapshotNIDFromEventID(%s) returned 0 NID, was this event stored?", eventID)
+	}
+
+	stateEntries, err := v.LoadStateAtSnapshot(ctx, snapshotNID)
+	if err != nil {
+		return nil, err
+	}
+
+	return stateEntries, nil
+}
+
 // LoadCombinedStateAfterEvents loads a snapshot of the state after each of the events
 // and combines those snapshots together into a single list. At this point it is
 // possible to run into duplicate (type, state key) tuples.
diff --git a/roomserver/storage/interface.go b/roomserver/storage/interface.go
index a98fda073..b12025c41 100644
--- a/roomserver/storage/interface.go
+++ b/roomserver/storage/interface.go
@@ -166,4 +166,6 @@ type Database interface {
 	GetKnownRooms(ctx context.Context) ([]string, error)
 	// ForgetRoom sets a flag in the membership table, that the user wishes to forget a specific room
 	ForgetRoom(ctx context.Context, userID, roomID string, forget bool) error
+
+	GetHistoryVisibilityState(ctx context.Context, roomInfo *types.RoomInfo, eventID string, domain string) ([]*gomatrixserverlib.Event, error)
 }
diff --git a/roomserver/storage/postgres/rooms_table.go b/roomserver/storage/postgres/rooms_table.go
index 24362af74..994399532 100644
--- a/roomserver/storage/postgres/rooms_table.go
+++ b/roomserver/storage/postgres/rooms_table.go
@@ -147,14 +147,16 @@ func (s *roomStatements) InsertRoomNID(
 func (s *roomStatements) SelectRoomInfo(ctx context.Context, txn *sql.Tx, roomID string) (*types.RoomInfo, error) {
 	var info types.RoomInfo
 	var latestNIDs pq.Int64Array
+	var stateSnapshotNID types.StateSnapshotNID
 	stmt := sqlutil.TxStmt(txn, s.selectRoomInfoStmt)
 	err := stmt.QueryRowContext(ctx, roomID).Scan(
-		&info.RoomVersion, &info.RoomNID, &info.StateSnapshotNID, &latestNIDs,
+		&info.RoomVersion, &info.RoomNID, &stateSnapshotNID, &latestNIDs,
 	)
 	if err == sql.ErrNoRows {
 		return nil, nil
 	}
-	info.IsStub = len(latestNIDs) == 0
+	info.SetStateSnapshotNID(stateSnapshotNID)
+	info.SetIsStub(len(latestNIDs) == 0)
 	return &info, err
 }
 
diff --git a/roomserver/storage/postgres/state_snapshot_table.go b/roomserver/storage/postgres/state_snapshot_table.go
index a24b7f3f0..99c76befe 100644
--- a/roomserver/storage/postgres/state_snapshot_table.go
+++ b/roomserver/storage/postgres/state_snapshot_table.go
@@ -72,9 +72,35 @@ const bulkSelectStateBlockNIDsSQL = "" +
 	"SELECT state_snapshot_nid, state_block_nids FROM roomserver_state_snapshots" +
 	" WHERE state_snapshot_nid = ANY($1) ORDER BY state_snapshot_nid ASC"
 
+// Looks up both the history visibility event and relevant membership events from
+// a given domain name from a given state snapshot. This is used to optimise the
+// helpers.CheckServerAllowedToSeeEvent function.
+// TODO: There's a sequence scan here because of the hash join strategy, which is
+// probably O(n) on state key entries, so there must be a way to avoid that somehow.
+// Event type NIDs are:
+// - 5: m.room.member as per https://github.com/matrix-org/dendrite/blob/c7f7aec4d07d59120d37d5b16a900f6d608a75c4/roomserver/storage/postgres/event_types_table.go#L40
+// - 7: m.room.history_visibility as per https://github.com/matrix-org/dendrite/blob/c7f7aec4d07d59120d37d5b16a900f6d608a75c4/roomserver/storage/postgres/event_types_table.go#L42
+const bulkSelectStateForHistoryVisibilitySQL = `
+	SELECT event_nid FROM (
+	  SELECT event_nid, event_type_nid, event_state_key_nid FROM roomserver_events
+	  WHERE (event_type_nid = 5 OR event_type_nid = 7)
+	  AND event_nid = ANY(
+	    SELECT UNNEST(event_nids) FROM roomserver_state_block
+	    WHERE state_block_nid = ANY(
+	      SELECT UNNEST(state_block_nids) FROM roomserver_state_snapshots
+	      WHERE state_snapshot_nid = $1
+	    )
+	  )
+	) AS roomserver_events
+	INNER JOIN roomserver_event_state_keys
+	  ON roomserver_events.event_state_key_nid = roomserver_event_state_keys.event_state_key_nid
+	  AND (event_type_nid = 7 OR event_state_key LIKE '%:' || $2);
+`
+
 type stateSnapshotStatements struct {
-	insertStateStmt              *sql.Stmt
-	bulkSelectStateBlockNIDsStmt *sql.Stmt
+	insertStateStmt                         *sql.Stmt
+	bulkSelectStateBlockNIDsStmt            *sql.Stmt
+	bulkSelectStateForHistoryVisibilityStmt *sql.Stmt
 }
 
 func CreateStateSnapshotTable(db *sql.DB) error {
@@ -88,6 +114,7 @@ func PrepareStateSnapshotTable(db *sql.DB) (tables.StateSnapshot, error) {
 	return s, sqlutil.StatementList{
 		{&s.insertStateStmt, insertStateSQL},
 		{&s.bulkSelectStateBlockNIDsStmt, bulkSelectStateBlockNIDsSQL},
+		{&s.bulkSelectStateForHistoryVisibilityStmt, bulkSelectStateForHistoryVisibilitySQL},
 	}.Prepare(db)
 }
 
@@ -136,3 +163,23 @@ func (s *stateSnapshotStatements) BulkSelectStateBlockNIDs(
 	}
 	return results, nil
 }
+
+func (s *stateSnapshotStatements) BulkSelectStateForHistoryVisibility(
+	ctx context.Context, txn *sql.Tx, stateSnapshotNID types.StateSnapshotNID, domain string,
+) ([]types.EventNID, error) {
+	stmt := sqlutil.TxStmt(txn, s.bulkSelectStateForHistoryVisibilityStmt)
+	rows, err := stmt.QueryContext(ctx, stateSnapshotNID, domain)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close() // nolint: errcheck
+	results := make([]types.EventNID, 0, 16)
+	for rows.Next() {
+		var eventNID types.EventNID
+		if err = rows.Scan(&eventNID); err != nil {
+			return nil, err
+		}
+		results = append(results, eventNID)
+	}
+	return results, rows.Err()
+}
diff --git a/roomserver/storage/shared/room_updater.go b/roomserver/storage/shared/room_updater.go
index c35ac653c..42c0c8f2d 100644
--- a/roomserver/storage/shared/room_updater.go
+++ b/roomserver/storage/shared/room_updater.go
@@ -217,6 +217,14 @@ func (u *RoomUpdater) SetLatestEvents(
 	roomNID types.RoomNID, latest []types.StateAtEventAndReference, lastEventNIDSent types.EventNID,
 	currentStateSnapshotNID types.StateSnapshotNID,
 ) error {
+	switch {
+	case len(latest) == 0:
+		return fmt.Errorf("cannot set latest events with no latest event references")
+	case currentStateSnapshotNID == 0:
+		return fmt.Errorf("cannot set latest events with invalid state snapshot NID")
+	case lastEventNIDSent == 0:
+		return fmt.Errorf("cannot set latest events with invalid latest event NID")
+	}
 	eventNIDs := make([]types.EventNID, len(latest))
 	for i := range latest {
 		eventNIDs[i] = latest[i].EventNID
@@ -229,8 +237,10 @@ func (u *RoomUpdater) SetLatestEvents(
 		// Since it's entirely possible that this types.RoomInfo came from the
 		// cache, we should make sure to update that entry so that the next run
 		// works from live data.
-		u.roomInfo.StateSnapshotNID = currentStateSnapshotNID
-		u.roomInfo.IsStub = false
+		if u.roomInfo != nil {
+			u.roomInfo.SetStateSnapshotNID(currentStateSnapshotNID)
+			u.roomInfo.SetIsStub(false)
+		}
 		return nil
 	})
 }
diff --git a/roomserver/storage/shared/storage.go b/roomserver/storage/shared/storage.go
index 2f9932ff8..9e6a4142c 100644
--- a/roomserver/storage/shared/storage.go
+++ b/roomserver/storage/shared/storage.go
@@ -156,15 +156,30 @@ func (d *Database) RoomInfo(ctx context.Context, roomID string) (*types.RoomInfo
 }
 
 func (d *Database) roomInfo(ctx context.Context, txn *sql.Tx, roomID string) (*types.RoomInfo, error) {
-	if roomInfo, ok := d.Cache.GetRoomInfo(roomID); ok && roomInfo != nil {
+	roomInfo, ok := d.Cache.GetRoomInfo(roomID)
+	if ok && roomInfo != nil && !roomInfo.IsStub() {
+		// The data that's in the cache is not stubby, so return it.
 		return roomInfo, nil
 	}
-	roomInfo, err := d.RoomsTable.SelectRoomInfo(ctx, txn, roomID)
-	if err == nil && roomInfo != nil {
-		d.Cache.StoreRoomServerRoomID(roomInfo.RoomNID, roomID)
-		d.Cache.StoreRoomInfo(roomID, roomInfo)
+	// At this point we either don't have an entry in the cache, or
+	// it is stubby, so let's check the roomserver_rooms table again.
+	roomInfoFromDB, err := d.RoomsTable.SelectRoomInfo(ctx, txn, roomID)
+	if err != nil {
+		return nil, err
 	}
-	return roomInfo, err
+	// If we have a stubby cache entry already, update it and return
+	// the reference to the cache entry.
+	if roomInfo != nil {
+		roomInfo.CopyFrom(roomInfoFromDB)
+		return roomInfo, nil
+	}
+	// Otherwise, try to admit the data into the cache and return the
+	// new reference from the database.
+	if roomInfoFromDB != nil {
+		d.Cache.StoreRoomServerRoomID(roomInfoFromDB.RoomNID, roomID)
+		d.Cache.StoreRoomInfo(roomID, roomInfoFromDB)
+	}
+	return roomInfoFromDB, err
 }
 
 func (d *Database) AddState(
@@ -676,7 +691,7 @@ func (d *Database) storeEvent(
 		succeeded := false
 		if updater == nil {
 			var roomInfo *types.RoomInfo
-			roomInfo, err = d.RoomInfo(ctx, event.RoomID())
+			roomInfo, err = d.roomInfo(ctx, txn, event.RoomID())
 			if err != nil {
 				return 0, 0, types.StateAtEvent{}, nil, "", fmt.Errorf("d.RoomInfo: %w", err)
 			}
@@ -988,6 +1003,38 @@ func (d *Database) loadEvent(ctx context.Context, eventID string) *types.Event {
 	return &evs[0]
 }
 
+func (d *Database) GetHistoryVisibilityState(ctx context.Context, roomInfo *types.RoomInfo, eventID string, domain string) ([]*gomatrixserverlib.Event, error) {
+	eventStates, err := d.EventsTable.BulkSelectStateAtEventByID(ctx, nil, []string{eventID})
+	if err != nil {
+		return nil, err
+	}
+	stateSnapshotNID := eventStates[0].BeforeStateSnapshotNID
+	if stateSnapshotNID == 0 {
+		return nil, nil
+	}
+	eventNIDs, err := d.StateSnapshotTable.BulkSelectStateForHistoryVisibility(ctx, nil, stateSnapshotNID, domain)
+	if err != nil {
+		return nil, err
+	}
+	eventIDs, _ := d.EventsTable.BulkSelectEventID(ctx, nil, eventNIDs)
+	if err != nil {
+		eventIDs = map[types.EventNID]string{}
+	}
+	events := make([]*gomatrixserverlib.Event, 0, len(eventNIDs))
+	for _, eventNID := range eventNIDs {
+		data, err := d.EventJSONTable.BulkSelectEventJSON(ctx, nil, []types.EventNID{eventNID})
+		if err != nil {
+			return nil, err
+		}
+		ev, err := gomatrixserverlib.NewEventFromTrustedJSONWithEventID(eventIDs[eventNID], data[0].EventJSON, false, roomInfo.RoomVersion)
+		if err != nil {
+			return nil, err
+		}
+		events = append(events, ev)
+	}
+	return events, nil
+}
+
 // GetStateEvent returns the current state event of a given type for a given room with a given state key
 // If no event could be found, returns nil
 // If there was an issue during the retrieval, returns an error
@@ -1000,7 +1047,7 @@ func (d *Database) GetStateEvent(ctx context.Context, roomID, evType, stateKey s
 		return nil, fmt.Errorf("room %s doesn't exist", roomID)
 	}
 	// e.g invited rooms
-	if roomInfo.IsStub {
+	if roomInfo.IsStub() {
 		return nil, nil
 	}
 	eventTypeNID, err := d.EventTypesTable.SelectEventTypeNID(ctx, nil, evType)
@@ -1019,7 +1066,7 @@ func (d *Database) GetStateEvent(ctx context.Context, roomID, evType, stateKey s
 	if err != nil {
 		return nil, err
 	}
-	entries, err := d.loadStateAtSnapshot(ctx, roomInfo.StateSnapshotNID)
+	entries, err := d.loadStateAtSnapshot(ctx, roomInfo.StateSnapshotNID())
 	if err != nil {
 		return nil, err
 	}
@@ -1065,7 +1112,7 @@ func (d *Database) GetStateEventsWithEventType(ctx context.Context, roomID, evTy
 		return nil, fmt.Errorf("room %s doesn't exist", roomID)
 	}
 	// e.g invited rooms
-	if roomInfo.IsStub {
+	if roomInfo.IsStub() {
 		return nil, nil
 	}
 	eventTypeNID, err := d.EventTypesTable.SelectEventTypeNID(ctx, nil, evType)
@@ -1076,7 +1123,7 @@ func (d *Database) GetStateEventsWithEventType(ctx context.Context, roomID, evTy
 	if err != nil {
 		return nil, err
 	}
-	entries, err := d.loadStateAtSnapshot(ctx, roomInfo.StateSnapshotNID)
+	entries, err := d.loadStateAtSnapshot(ctx, roomInfo.StateSnapshotNID())
 	if err != nil {
 		return nil, err
 	}
@@ -1193,10 +1240,10 @@ func (d *Database) GetBulkStateContent(ctx context.Context, roomIDs []string, tu
 			return nil, fmt.Errorf("GetBulkStateContent: failed to load room info for room %s : %w", roomID, err2)
 		}
 		// for unknown rooms or rooms which we don't have the current state, skip them.
-		if roomInfo == nil || roomInfo.IsStub {
+		if roomInfo == nil || roomInfo.IsStub() {
 			continue
 		}
-		entries, err2 := d.loadStateAtSnapshot(ctx, roomInfo.StateSnapshotNID)
+		entries, err2 := d.loadStateAtSnapshot(ctx, roomInfo.StateSnapshotNID())
 		if err2 != nil {
 			return nil, fmt.Errorf("GetBulkStateContent: failed to load state for room %s : %w", roomID, err2)
 		}
diff --git a/roomserver/storage/sqlite3/rooms_table.go b/roomserver/storage/sqlite3/rooms_table.go
index 03ad4b3d0..25b611b3e 100644
--- a/roomserver/storage/sqlite3/rooms_table.go
+++ b/roomserver/storage/sqlite3/rooms_table.go
@@ -129,9 +129,10 @@ func (s *roomStatements) SelectRoomIDsWithEvents(ctx context.Context, txn *sql.T
 func (s *roomStatements) SelectRoomInfo(ctx context.Context, txn *sql.Tx, roomID string) (*types.RoomInfo, error) {
 	var info types.RoomInfo
 	var latestNIDsJSON string
+	var stateSnapshotNID types.StateSnapshotNID
 	stmt := sqlutil.TxStmt(txn, s.selectRoomInfoStmt)
 	err := stmt.QueryRowContext(ctx, roomID).Scan(
-		&info.RoomVersion, &info.RoomNID, &info.StateSnapshotNID, &latestNIDsJSON,
+		&info.RoomVersion, &info.RoomNID, &stateSnapshotNID, &latestNIDsJSON,
 	)
 	if err != nil {
 		if err == sql.ErrNoRows {
@@ -143,7 +144,8 @@ func (s *roomStatements) SelectRoomInfo(ctx context.Context, txn *sql.Tx, roomID
 	if err = json.Unmarshal([]byte(latestNIDsJSON), &latestNIDs); err != nil {
 		return nil, err
 	}
-	info.IsStub = len(latestNIDs) == 0
+	info.SetStateSnapshotNID(stateSnapshotNID)
+	info.SetIsStub(len(latestNIDs) == 0)
 	return &info, err
 }
 
diff --git a/roomserver/storage/sqlite3/state_snapshot_table.go b/roomserver/storage/sqlite3/state_snapshot_table.go
index b8136b758..73827522c 100644
--- a/roomserver/storage/sqlite3/state_snapshot_table.go
+++ b/roomserver/storage/sqlite3/state_snapshot_table.go
@@ -140,3 +140,9 @@ func (s *stateSnapshotStatements) BulkSelectStateBlockNIDs(
 	}
 	return results, nil
 }
+
+func (s *stateSnapshotStatements) BulkSelectStateForHistoryVisibility(
+	ctx context.Context, txn *sql.Tx, stateSnapshotNID types.StateSnapshotNID, domain string,
+) ([]types.EventNID, error) {
+	return nil, tables.OptimisationNotSupportedError
+}
diff --git a/roomserver/storage/tables/interface.go b/roomserver/storage/tables/interface.go
index d228257b7..58c43ac45 100644
--- a/roomserver/storage/tables/interface.go
+++ b/roomserver/storage/tables/interface.go
@@ -3,12 +3,15 @@ package tables
 import (
 	"context"
 	"database/sql"
+	"errors"
 
 	"github.com/matrix-org/dendrite/roomserver/types"
 	"github.com/matrix-org/gomatrixserverlib"
 	"github.com/tidwall/gjson"
 )
 
+var OptimisationNotSupportedError = errors.New("optimisation not supported")
+
 type EventJSONPair struct {
 	EventNID  types.EventNID
 	EventJSON []byte
@@ -80,6 +83,10 @@ type Rooms interface {
 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, txn *sql.Tx, stateNIDs []types.StateSnapshotNID) ([]types.StateBlockNIDList, error)
+	// BulkSelectStateForHistoryVisibility is a PostgreSQL-only optimisation for finding
+	// which users are in a room faster than having to load the entire room state. In the
+	// case of SQLite, this will return tables.OptimisationNotSupportedError.
+	BulkSelectStateForHistoryVisibility(ctx context.Context, txn *sql.Tx, stateSnapshotNID types.StateSnapshotNID, domain string) ([]types.EventNID, error)
 }
 
 type StateBlock interface {
diff --git a/roomserver/storage/tables/rooms_table_test.go b/roomserver/storage/tables/rooms_table_test.go
index 0a02369a1..eddd012c8 100644
--- a/roomserver/storage/tables/rooms_table_test.go
+++ b/roomserver/storage/tables/rooms_table_test.go
@@ -63,12 +63,12 @@ func TestRoomsTable(t *testing.T) {
 
 		roomInfo, err := tab.SelectRoomInfo(ctx, nil, room.ID)
 		assert.NoError(t, err)
-		assert.Equal(t, &types.RoomInfo{
-			RoomNID:          wantRoomNID,
-			RoomVersion:      room.Version,
-			StateSnapshotNID: 0,
-			IsStub:           true, // there are no latestEventNIDs
-		}, roomInfo)
+		expected := &types.RoomInfo{
+			RoomNID:     wantRoomNID,
+			RoomVersion: room.Version,
+		}
+		expected.SetIsStub(true) // there are no latestEventNIDs
+		assert.Equal(t, expected, roomInfo)
 
 		roomInfo, err = tab.SelectRoomInfo(ctx, nil, "!doesnotexist:localhost")
 		assert.NoError(t, err)
@@ -103,12 +103,12 @@ func TestRoomsTable(t *testing.T) {
 
 		roomInfo, err = tab.SelectRoomInfo(ctx, nil, room.ID)
 		assert.NoError(t, err)
-		assert.Equal(t, &types.RoomInfo{
-			RoomNID:          wantRoomNID,
-			RoomVersion:      room.Version,
-			StateSnapshotNID: 1,
-			IsStub:           false,
-		}, roomInfo)
+		expected = &types.RoomInfo{
+			RoomNID:     wantRoomNID,
+			RoomVersion: room.Version,
+		}
+		expected.SetStateSnapshotNID(1)
+		assert.Equal(t, expected, roomInfo)
 
 		eventNIDs, snapshotNID, err := tab.SelectLatestEventNIDs(ctx, nil, wantRoomNID)
 		assert.NoError(t, err)
diff --git a/roomserver/storage/tables/state_snapshot_table_test.go b/roomserver/storage/tables/state_snapshot_table_test.go
index dcdb5d8f1..b2e59377d 100644
--- a/roomserver/storage/tables/state_snapshot_table_test.go
+++ b/roomserver/storage/tables/state_snapshot_table_test.go
@@ -23,6 +23,15 @@ func mustCreateStateSnapshotTable(t *testing.T, dbType test.DBType) (tab tables.
 	assert.NoError(t, err)
 	switch dbType {
 	case test.DBTypePostgres:
+		// for the PostgreSQL history visibility optimisation to work,
+		// we also need some other tables to exist
+		err = postgres.CreateEventStateKeysTable(db)
+		assert.NoError(t, err)
+		err = postgres.CreateEventsTable(db)
+		assert.NoError(t, err)
+		err = postgres.CreateStateBlockTable(db)
+		assert.NoError(t, err)
+		// ... and then the snapshot table itself
 		err = postgres.CreateStateSnapshotTable(db)
 		assert.NoError(t, err)
 		tab, err = postgres.PrepareStateSnapshotTable(db)
diff --git a/roomserver/types/types.go b/roomserver/types/types.go
index bc01ca33c..f40980994 100644
--- a/roomserver/types/types.go
+++ b/roomserver/types/types.go
@@ -19,6 +19,7 @@ import (
 	"encoding/json"
 	"sort"
 	"strings"
+	"sync"
 
 	"github.com/matrix-org/gomatrixserverlib"
 	"github.com/matrix-org/util"
@@ -279,8 +280,46 @@ func (e RejectedError) Error() string { return string(e) }
 
 // RoomInfo contains metadata about a room
 type RoomInfo struct {
+	mu               sync.RWMutex
 	RoomNID          RoomNID
 	RoomVersion      gomatrixserverlib.RoomVersion
-	StateSnapshotNID StateSnapshotNID
-	IsStub           bool
+	stateSnapshotNID StateSnapshotNID
+	isStub           bool
+}
+
+func (r *RoomInfo) StateSnapshotNID() StateSnapshotNID {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+	return r.stateSnapshotNID
+}
+
+func (r *RoomInfo) IsStub() bool {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+	return r.isStub
+}
+
+func (r *RoomInfo) SetStateSnapshotNID(nid StateSnapshotNID) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	r.stateSnapshotNID = nid
+}
+
+func (r *RoomInfo) SetIsStub(isStub bool) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	r.isStub = isStub
+}
+
+func (r *RoomInfo) CopyFrom(r2 *RoomInfo) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+
+	r2.mu.RLock()
+	defer r2.mu.RUnlock()
+
+	r.RoomNID = r2.RoomNID
+	r.RoomVersion = r2.RoomVersion
+	r.stateSnapshotNID = r2.stateSnapshotNID
+	r.isStub = r2.isStub
 }
diff --git a/setup/base/base.go b/setup/base/base.go
index 5a64f8797..b84f5362b 100644
--- a/setup/base/base.go
+++ b/setup/base/base.go
@@ -383,6 +383,25 @@ func (b *BaseDendrite) CreateFederationClient() *gomatrixserverlib.FederationCli
 	return client
 }
 
+func (b *BaseDendrite) configureHTTPErrors() {
+	notAllowedHandler := func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusMethodNotAllowed)
+		_, _ = w.Write([]byte(fmt.Sprintf("405 %s not allowed on this endpoint", r.Method)))
+	}
+
+	notFoundCORSHandler := httputil.WrapHandlerInCORS(http.NotFoundHandler())
+	notAllowedCORSHandler := httputil.WrapHandlerInCORS(http.HandlerFunc(notAllowedHandler))
+
+	for _, router := range []*mux.Router{
+		b.PublicClientAPIMux, b.PublicMediaAPIMux,
+		b.DendriteAdminMux, b.SynapseAdminMux,
+		b.PublicWellKnownAPIMux,
+	} {
+		router.NotFoundHandler = notFoundCORSHandler
+		router.MethodNotAllowedHandler = notAllowedCORSHandler
+	}
+}
+
 // SetupAndServeHTTP sets up the HTTP server to serve endpoints registered on
 // ApiMux under /api/ and adds a prometheus handler under /metrics.
 func (b *BaseDendrite) SetupAndServeHTTP(
@@ -423,6 +442,8 @@ func (b *BaseDendrite) SetupAndServeHTTP(
 		}
 	}
 
+	b.configureHTTPErrors()
+
 	internalRouter.PathPrefix(httputil.InternalPathPrefix).Handler(b.InternalAPIMux)
 	if b.Cfg.Global.Metrics.Enabled {
 		internalRouter.Handle("/metrics", httputil.WrapHandlerInBasicAuth(promhttp.Handler(), b.Cfg.Global.Metrics.BasicAuth))
diff --git a/setup/config/config_jetstream.go b/setup/config/config_jetstream.go
index e4cfd4d3b..a7827597e 100644
--- a/setup/config/config_jetstream.go
+++ b/setup/config/config_jetstream.go
@@ -17,6 +17,10 @@ type JetStream struct {
 	TopicPrefix string `yaml:"topic_prefix"`
 	// Keep all storage in memory. This is mostly useful for unit tests.
 	InMemory bool `yaml:"in_memory"`
+	// Disable logging. This is mostly useful for unit tests.
+	NoLog bool `yaml:"-"`
+	// Disables TLS validation. This should NOT be used in production
+	DisableTLSValidation bool `yaml:"disable_tls_validation"`
 }
 
 func (c *JetStream) Prefixed(name string) string {
@@ -32,6 +36,8 @@ func (c *JetStream) Defaults(generate bool) {
 	c.TopicPrefix = "Dendrite"
 	if generate {
 		c.StoragePath = Path("./")
+		c.NoLog = true
+		c.DisableTLSValidation = true
 	}
 }
 
diff --git a/setup/jetstream/nats.go b/setup/jetstream/nats.go
index 5359b4581..051d55a35 100644
--- a/setup/jetstream/nats.go
+++ b/setup/jetstream/nats.go
@@ -1,6 +1,7 @@
 package jetstream
 
 import (
+	"crypto/tls"
 	"fmt"
 	"reflect"
 	"strings"
@@ -46,6 +47,7 @@ func (s *NATSInstance) Prepare(process *process.ProcessContext, cfg *config.JetS
 			NoSystemAccount: true,
 			MaxPayload:      16 * 1024 * 1024,
 			NoSigs:          true,
+			NoLog:           cfg.NoLog,
 		})
 		if err != nil {
 			panic(err)
@@ -75,7 +77,13 @@ func (s *NATSInstance) Prepare(process *process.ProcessContext, cfg *config.JetS
 func setupNATS(process *process.ProcessContext, cfg *config.JetStream, nc *natsclient.Conn) (natsclient.JetStreamContext, *natsclient.Conn) {
 	if nc == nil {
 		var err error
-		nc, err = natsclient.Connect(strings.Join(cfg.Addresses, ","))
+		opts := []natsclient.Option{}
+		if cfg.DisableTLSValidation {
+			opts = append(opts, natsclient.Secure(&tls.Config{
+				InsecureSkipVerify: true,
+			}))
+		}
+		nc, err = natsclient.Connect(strings.Join(cfg.Addresses, ","), opts...)
 		if err != nil {
 			logrus.WithError(err).Panic("Unable to connect to NATS")
 			return nil, nil
diff --git a/syncapi/streams/stream_pdu.go b/syncapi/streams/stream_pdu.go
index 00b3dfe3b..1003208fd 100644
--- a/syncapi/streams/stream_pdu.go
+++ b/syncapi/streams/stream_pdu.go
@@ -109,12 +109,11 @@ func (p *PDUStreamProvider) CompleteSync(
 		p.queue(func() {
 			defer reqWaitGroup.Done()
 
-			var jr *types.JoinResponse
-			jr, err = p.getJoinResponseForCompleteSync(
+			jr, jerr := p.getJoinResponseForCompleteSync(
 				ctx, roomID, r, &stateFilter, &eventFilter, req.WantFullState, req.Device,
 			)
-			if err != nil {
-				req.Log.WithError(err).Error("p.getJoinResponseForCompleteSync failed")
+			if jerr != nil {
+				req.Log.WithError(jerr).Error("p.getJoinResponseForCompleteSync failed")
 				return
 			}
 
@@ -262,9 +261,9 @@ func (p *PDUStreamProvider) addRoomDeltaToResponse(
 		var pos types.StreamPosition
 		if _, pos, err = p.DB.PositionInTopology(ctx, mostRecentEventID); err == nil {
 			switch {
-			case r.Backwards && pos > latestPosition:
+			case r.Backwards && pos < latestPosition:
 				fallthrough
-			case !r.Backwards && pos < latestPosition:
+			case !r.Backwards && pos > latestPosition:
 				latestPosition = pos
 			}
 		}
diff --git a/syncapi/sync/requestpool_test.go b/syncapi/sync/requestpool_test.go
index 5142f5dd3..3e5769d8c 100644
--- a/syncapi/sync/requestpool_test.go
+++ b/syncapi/sync/requestpool_test.go
@@ -128,19 +128,15 @@ func TestRequestPool_updatePresence(t *testing.T) {
 	go rp.cleanPresence(db, time.Millisecond*50)
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			beforeCount := func() int {
-				publisher.lock.Lock()
-				defer publisher.lock.Unlock()
-				return publisher.count
-			}()
+			publisher.lock.Lock()
+			beforeCount := publisher.count
+			publisher.lock.Unlock()
 			rp.updatePresence(db, tt.args.presence, tt.args.userID)
-			func() {
-				publisher.lock.Lock()
-				defer publisher.lock.Unlock()
-				if tt.wantIncrease && publisher.count <= beforeCount {
-					t.Fatalf("expected count to increase: %d <= %d", publisher.count, beforeCount)
-				}
-			}()
+			publisher.lock.Lock()
+			if tt.wantIncrease && publisher.count <= beforeCount {
+				t.Fatalf("expected count to increase: %d <= %d", publisher.count, beforeCount)
+			}
+			publisher.lock.Unlock()
 			time.Sleep(tt.args.sleep)
 		})
 	}
diff --git a/sytest-blacklist b/sytest-blacklist
index bcc345f6e..e0b2767b1 100644
--- a/sytest-blacklist
+++ b/sytest-blacklist
@@ -49,3 +49,7 @@ Notifications can be viewed with GET /notifications
 
 If remote user leaves room we no longer receive device updates
 Guest users can join guest_access rooms
+
+# You'll be shocked to discover this is flakey too
+
+Inbound /v1/send_join rejects joins from other servers