Definitely. They even let you export the password hashes (which you should do carefully). You can then import them into any identity provider that supports modified scrypt[0]. Your users will continue to be able to log in without a password reset.

0: https://firebase.google.com/docs/reference/admin/java/refere...

On certain databases, yes

We only scanned for firestore, which is a NoSQL database, conversion tools may still be possible, a good firebase alternative would be https://supabase.com, but please set up RLS, its IMO much easier then Firebase.

Wouldn't it be easy to migrate a NoSQL database to Postgres without any adaptation?

Postgres is an "object database", so you could use Array, JSON or JSONB fields wherever necessary, and you shouldn't introduce any foreign key relations or such.

It would, except if you have a f'ed up schema like most of these companies had.

The point is that Postgres has no problem at all with a fucked-up schema. You just tell it not to check a thing, and it won't check a thing.

But then, I may be underestimating how fucked-up things are.

The closest setup off the top of my head might be something like meteor.js on top of mongo DB.

Would work! If you're willing to write something, go for it. I'm personally way too exhausted right now.