diff --git a/changelog.d/10903.misc b/changelog.d/10903.misc
new file mode 100644
index 0000000000..2716ccb08c
--- /dev/null
+++ b/changelog.d/10903.misc
@@ -0,0 +1 @@
+Drop old functionality which maintained database compatibility with Synapse versions before 1.31.
diff --git a/synapse/storage/databases/main/events.py b/synapse/storage/databases/main/events.py
index 584f818ff3..cc4e31ec30 100644
--- a/synapse/storage/databases/main/events.py
+++ b/synapse/storage/databases/main/events.py
@@ -1276,13 +1276,6 @@ class PersistEventsStore:
                     logger.exception("")
                     raise
 
-                # update the stored internal_metadata to update the "outlier" flag.
-                # TODO: This is unused as of Synapse 1.31. Remove it once we are happy
-                #  to drop backwards-compatibility with 1.30.
-                metadata_json = json_encoder.encode(event.internal_metadata.get_dict())
-                sql = "UPDATE event_json SET internal_metadata = ? WHERE event_id = ?"
-                txn.execute(sql, (metadata_json, event.event_id))
-
                 # Add an entry to the ex_outlier_stream table to replicate the
                 # change in outlier status to our workers.
                 stream_order = event.internal_metadata.stream_ordering
@@ -1327,19 +1320,6 @@ class PersistEventsStore:
             d.pop("redacted_because", None)
             return d
 
-        def get_internal_metadata(event):
-            im = event.internal_metadata.get_dict()
-
-            # temporary hack for database compatibility with Synapse 1.30 and earlier:
-            # store the `outlier` flag inside the internal_metadata json as well as in
-            # the `events` table, so that if anyone rolls back to an older Synapse,
-            # things keep working. This can be removed once we are happy to drop support
-            # for that
-            if event.internal_metadata.is_outlier():
-                im["outlier"] = True
-
-            return im
-
         self.db_pool.simple_insert_many_txn(
             txn,
             table="event_json",
@@ -1348,7 +1328,7 @@ class PersistEventsStore:
                     "event_id": event.event_id,
                     "room_id": event.room_id,
                     "internal_metadata": json_encoder.encode(
-                        get_internal_metadata(event)
+                        event.internal_metadata.get_dict()
                     ),
                     "json": json_encoder.encode(event_dict(event)),
                     "format_version": event.format_version,
diff --git a/synapse/storage/schema/__init__.py b/synapse/storage/schema/__init__.py
index 573e05a482..1aee741a8b 100644
--- a/synapse/storage/schema/__init__.py
+++ b/synapse/storage/schema/__init__.py
@@ -12,9 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-# When updating these values, please leave a short summary of the changes below.
-
-SCHEMA_VERSION = 64
+SCHEMA_VERSION = 64  # remember to update the list below when updating
 """Represents the expectations made by the codebase about the database schema
 
 This should be incremented whenever the codebase changes its requirements on the
@@ -46,7 +44,7 @@ Changes in SCHEMA_VERSION = 64:
 """
 
 
-SCHEMA_COMPAT_VERSION = 59
+SCHEMA_COMPAT_VERSION = 60  # 60: "outlier" not in internal_metadata.
 """Limit on how far the synapse codebase can be rolled back without breaking db compat
 
 This value is stored in the database, and checked on startup. If the value in the