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/roomserver/internal/input/input_missing.go b/roomserver/internal/input/input_missing.go
index edc153b7f..1fe25e38a 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)
diff --git a/roomserver/internal/query/query.go b/roomserver/internal/query/query.go
index 50fc98ed2..c41e1ea67 100644
--- a/roomserver/internal/query/query.go
+++ b/roomserver/internal/query/query.go
@@ -399,8 +399,8 @@ 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,
diff --git a/roomserver/storage/shared/room_updater.go b/roomserver/storage/shared/room_updater.go
index a7ae26d43..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.SetStateSnapshotNID(currentStateSnapshotNID)
-		u.roomInfo.SetIsStub(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 05b897149..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)
 			}
diff --git a/roomserver/types/types.go b/roomserver/types/types.go
index 726659ea0..f40980994 100644
--- a/roomserver/types/types.go
+++ b/roomserver/types/types.go
@@ -310,3 +310,16 @@ func (r *RoomInfo) SetIsStub(isStub bool) {
 	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
+}