Incidentally, the problem in HierCachedModel is that changes to records (in a save override), invalidates cached values in related records, so caches are deleted for all relations, and to do that, it traverses those relations to get the cache record IDs (<class>.<pk>.<fieldname>). Skipping those operations has no downside, as there is with MaintainedModel. If the relations don’t exist, there are no caches to delete.