Offload more work to database replica

src/pretix/helpers/database.py

@@ -76,3 +76,21 @@ class GroupConcat(Aggregate):
             function='string_agg',
             template="%(function)s(%(field)s::text, '%(separator)s')",
         )
+
+
+class ReplicaRouter:
+
+    def db_for_read(self, model, **hints):
+        return 'default'
+
+    def db_for_write(self, model, **hints):
+        return 'default'
+
+    def allow_relation(self, obj1, obj2, **hints):
+        db_list = ('default', 'replica')
+        if obj1._state.db in db_list and obj2._state.db in db_list:
+            return True
+        return None
+
+    def allow_migrate(self, db, app_label, model_name=None, **hintrs):
+        return True