Like the opposite of a cloud database. An anti-RDS. The third party is just an orchestrator for your local auth system. I'd be curious to see how that works.

At the least, though, it would need 'you' to be pretty good at securing your now-publicly-accessible database resource. Perhaps there is a middle ground where the auth provider specifies an 'interface' (eg via OpenAPI) and 'you' provide a set of endpoints to fulfil that spec; a protective shield over the database which remains locked down internally.

Reversing the flow; an interesting idea.