diff --git a/roomserver/storage/postgres/state_snapshot_table.go b/roomserver/storage/postgres/state_snapshot_table.go
index 527b714a6..26ebcf856 100644
--- a/roomserver/storage/postgres/state_snapshot_table.go
+++ b/roomserver/storage/postgres/state_snapshot_table.go
@@ -77,22 +77,21 @@ const bulkSelectStateBlockNIDsSQL = "" +
 // 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.
-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);
-`
+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
diff --git a/roomserver/storage/sqlite3/state_snapshot_table.go b/roomserver/storage/sqlite3/state_snapshot_table.go
index d2b2875ae..6cc783bfc 100644
--- a/roomserver/storage/sqlite3/state_snapshot_table.go
+++ b/roomserver/storage/sqlite3/state_snapshot_table.go
@@ -62,10 +62,32 @@ const bulkSelectStateBlockNIDsSQL = "" +
 	"SELECT state_snapshot_nid, state_block_nids FROM roomserver_state_snapshots" +
 	" WHERE state_snapshot_nid IN ($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.
+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 {
-	db                           *sql.DB
-	insertStateStmt              *sql.Stmt
-	bulkSelectStateBlockNIDsStmt *sql.Stmt
+	db                                      *sql.DB
+	insertStateStmt                         *sql.Stmt
+	bulkSelectStateBlockNIDsStmt            *sql.Stmt
+	bulkSelectStateForHistoryVisibilityStmt *sql.Stmt
 }
 
 func CreateStateSnapshotTable(db *sql.DB) error {
@@ -81,6 +103,7 @@ func PrepareStateSnapshotTable(db *sql.DB) (tables.StateSnapshot, error) {
 	return s, sqlutil.StatementList{
 		{&s.insertStateStmt, insertStateSQL},
 		{&s.bulkSelectStateBlockNIDsStmt, bulkSelectStateBlockNIDsSQL},
+		{&s.bulkSelectStateForHistoryVisibilityStmt, bulkSelectStateForHistoryVisibilitySQL},
 	}.Prepare(db)
 }
 
@@ -144,5 +167,22 @@ func (s *stateSnapshotStatements) BulkSelectStateBlockNIDs(
 func (s *stateSnapshotStatements) BulkSelectStateForHistoryVisibility(
 	ctx context.Context, txn *sql.Tx, stateSnapshotNID types.StateSnapshotNID, domain string,
 ) ([]types.EventNID, error) {
-	return nil, nil
+	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 i := 0; rows.Next(); i++ {
+		var eventNID types.EventNID
+		if err = rows.Scan(&eventNID); err != nil {
+			return nil, err
+		}
+		results = append(results, eventNID)
+	}
+	if err = rows.Err(); err != nil {
+		return nil, err
+	}
+	return results, nil
 }