diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index ff44c42312..d3823e24de 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -944,7 +944,7 @@ class FederationHandler(BaseHandler):
             marker_event,
         )
 
-        await self.store.insert_backward_extremity(
+        await self.store.insert_insertion_extremity(
             insertion_event_id, marker_event.room_id
         )
 
diff --git a/synapse/storage/databases/main/event_federation.py b/synapse/storage/databases/main/event_federation.py
index 8bbdb06c74..e8d513fbdd 100644
--- a/synapse/storage/databases/main/event_federation.py
+++ b/synapse/storage/databases/main/event_federation.py
@@ -692,7 +692,7 @@ class EventFederationWorkerStore(EventsWorkerStore, SignatureWorkerStore, SQLBas
             sql = """
                 SELECT b.event_id, MAX(e.depth) FROM insertion_events as i
                 /* We only want insertion events that are also marked as backwards extremities */
-                INNER JOIN event_backward_extremities as b USING (event_id)
+                INNER JOIN insertion_event_extremities as b USING (event_id)
                 /* Get the depth of the insertion event from the events table */
                 INNER JOIN events AS e USING (event_id)
                 WHERE b.room_id = ?
@@ -1144,11 +1144,11 @@ class EventFederationWorkerStore(EventsWorkerStore, SignatureWorkerStore, SQLBas
             _delete_old_forward_extrem_cache_txn,
         )
 
-    async def insert_backward_extremity(self, event_id: str, room_id: str) -> None:
-        def _insert_backward_extremity_txn(txn):
+    async def insert_insertion_extremity(self, event_id: str, room_id: str) -> None:
+        def _insert_insertion_extremity_txn(txn):
             self.db_pool.simple_insert_txn(
                 txn,
-                table="event_backward_extremities",
+                table="insertion_event_extremities",
                 values={
                     "event_id": event_id,
                     "room_id": room_id,
@@ -1156,7 +1156,7 @@ class EventFederationWorkerStore(EventsWorkerStore, SignatureWorkerStore, SQLBas
             )
 
         await self.db_pool.runInteraction(
-            "_insert_backward_extremity_txn", _insert_backward_extremity_txn
+            "_insert_insertion_extremity_txn", _insert_insertion_extremity_txn
         )
 
     async def insert_received_event_to_staging(
diff --git a/synapse/storage/databases/main/events.py b/synapse/storage/databases/main/events.py
index 2041d49a10..8651f374e4 100644
--- a/synapse/storage/databases/main/events.py
+++ b/synapse/storage/databases/main/events.py
@@ -1831,6 +1831,18 @@ class PersistEventsStore:
             },
         )
 
+        # When we receive an event with a `chunk_id` referencing the
+        # `next_chunk_id` of the insertion event, we can remove it from the
+        # `insertion_event_extremities` table.
+        sql = """
+            DELETE FROM insertion_event_extremities WHERE event_id IN (
+                SELECT event_id FROM insertion_events
+                WHERE next_chunk_id = ?
+            )
+        """
+
+        txn.execute(sql, (chunk_id,))
+
     def _handle_redaction(self, txn, redacted_event_id):
         """Handles receiving a redaction and checking whether we need to remove
         any redacted relations from the database.
diff --git a/synapse/storage/schema/main/delta/61/01insertion_event_lookups.sql b/synapse/storage/schema/main/delta/61/01insertion_event_lookups.sql
index 9f00b037a4..2d33663b00 100644
--- a/synapse/storage/schema/main/delta/61/01insertion_event_lookups.sql
+++ b/synapse/storage/schema/main/delta/61/01insertion_event_lookups.sql
@@ -40,6 +40,16 @@ CREATE INDEX IF NOT EXISTS insertion_event_edges_insertion_room_id ON insertion_
 CREATE INDEX IF NOT EXISTS insertion_event_edges_event_id ON insertion_event_edges(event_id);
 CREATE INDEX IF NOT EXISTS insertion_event_edges_insertion_prev_event_id ON insertion_event_edges(insertion_prev_event_id);
 
+-- Add a table that keeps track of which "insertion" events need to be backfilled
+CREATE TABLE IF NOT EXISTS insertion_event_extremities(
+    event_id TEXT NOT NULL,
+    room_id TEXT NOT NULL,
+    UNIQUE (event_id)
+);
+
+CREATE INDEX IF NOT EXISTS insertion_event_extremities_event_id ON insertion_event_extremities(event_id);
+CREATE INDEX IF NOT EXISTS insertion_event_extremities_room_id ON insertion_event_extremities(room_id);
+
 -- Add a table that keeps track of how each chunk is labeled. The chunks are
 -- connected together based insertion points `next_chunk_id`.
 CREATE TABLE IF NOT EXISTS chunk_edges(