Django ORM is great if you want it to manage your entire data model and are OK with living entirely within it's little world. But it can't support even basic stuff like composite primary keys, complex filters in a join clause, or any kind of lateral joins at all. It's also among the biggest offenders at hidden (and explosive) N+1s all over your codebase and templates unless you pay very special care. Also, the SQL it generates is usually very naive and often-times just not even performant.