diff --git a/changelog.d/17724.misc b/changelog.d/17724.misc
new file mode 100644
index 000000000..630443f17
--- /dev/null
+++ b/changelog.d/17724.misc
@@ -0,0 +1 @@
+Shortcut for checking if certain background updates have completed (utilized in Sliding Sync).
diff --git a/synapse/storage/background_updates.py b/synapse/storage/background_updates.py
index 1194b58ff..34139f580 100644
--- a/synapse/storage/background_updates.py
+++ b/synapse/storage/background_updates.py
@@ -490,6 +490,12 @@ class BackgroundUpdater:
         if self._all_done:
             return True
 
+        # We now check if we have completed all pending background updates. We
+        # do this as once this returns True then it will set `self._all_done`
+        # and we can skip checking the database in future.
+        if await self.has_completed_background_updates():
+            return True
+
         rows = await self.db_pool.simple_select_many_batch(
             table="background_updates",
             column="update_name",