diff --git a/changelog.d/11339.misc b/changelog.d/11339.misc
new file mode 100644
index 000000000..86594a332
--- /dev/null
+++ b/changelog.d/11339.misc
@@ -0,0 +1 @@
+Add type hints to storage classes.
diff --git a/mypy.ini b/mypy.ini
index d07273e63..710b1f3a4 100644
--- a/mypy.ini
+++ b/mypy.ini
@@ -28,7 +28,6 @@ exclude = (?x)
    |synapse/storage/databases/main/account_data.py
    |synapse/storage/databases/main/cache.py
    |synapse/storage/databases/main/devices.py
-   |synapse/storage/databases/main/directory.py
    |synapse/storage/databases/main/e2e_room_keys.py
    |synapse/storage/databases/main/end_to_end_keys.py
    |synapse/storage/databases/main/event_federation.py
@@ -177,6 +176,9 @@ disallow_untyped_defs = True
 [mypy-synapse.storage.databases.main.client_ips]
 disallow_untyped_defs = True
 
+[mypy-synapse.storage.databases.main.directory]
+disallow_untyped_defs = True
+
 [mypy-synapse.storage.databases.main.room_batch]
 disallow_untyped_defs = True
 
diff --git a/synapse/storage/databases/main/__init__.py b/synapse/storage/databases/main/__init__.py
index e22aa0b9b..9ff2d8d8c 100644
--- a/synapse/storage/databases/main/__init__.py
+++ b/synapse/storage/databases/main/__init__.py
@@ -154,6 +154,7 @@ class DataStore(
             db_conn, "local_group_updates", "stream_id"
         )
 
+        self._cache_id_gen: Optional[MultiWriterIdGenerator]
         if isinstance(self.database_engine, PostgresEngine):
             # We set the `writers` to an empty list here as we don't care about
             # missing updates over restarts, as we'll not have anything in our
diff --git a/synapse/storage/databases/main/directory.py b/synapse/storage/databases/main/directory.py
index 25131b1ea..a3442814d 100644
--- a/synapse/storage/databases/main/directory.py
+++ b/synapse/storage/databases/main/directory.py
@@ -13,18 +13,18 @@
 # limitations under the License.
 
 from collections import namedtuple
-from typing import Iterable, List, Optional
+from typing import Iterable, List, Optional, Tuple
 
 from synapse.api.errors import SynapseError
-from synapse.storage._base import SQLBaseStore
 from synapse.storage.database import LoggingTransaction
+from synapse.storage.databases.main import CacheInvalidationWorkerStore
 from synapse.types import RoomAlias
 from synapse.util.caches.descriptors import cached
 
 RoomAliasMapping = namedtuple("RoomAliasMapping", ("room_id", "room_alias", "servers"))
 
 
-class DirectoryWorkerStore(SQLBaseStore):
+class DirectoryWorkerStore(CacheInvalidationWorkerStore):
     async def get_association_from_room_alias(
         self, room_alias: RoomAlias
     ) -> Optional[RoomAliasMapping]:
@@ -92,7 +92,7 @@ class DirectoryWorkerStore(SQLBaseStore):
             creator: Optional user_id of creator.
         """
 
-        def alias_txn(txn):
+        def alias_txn(txn: LoggingTransaction) -> None:
             self.db_pool.simple_insert_txn(
                 txn,
                 "room_aliases",
@@ -176,9 +176,9 @@ class DirectoryStore(DirectoryWorkerStore):
                 If None, the creator will be left unchanged.
         """
 
-        def _update_aliases_for_room_txn(txn):
+        def _update_aliases_for_room_txn(txn: LoggingTransaction) -> None:
             update_creator_sql = ""
-            sql_params = (new_room_id, old_room_id)
+            sql_params: Tuple[str, ...] = (new_room_id, old_room_id)
             if creator:
                 update_creator_sql = ", creator = ?"
                 sql_params = (new_room_id, creator, old_room_id)