Supabase

Supabase builds on Postgres, one of the most mature open-source relational databases, making it a genuine alternative to Firebase for teams who value SQL. The auto-generated REST and GraphQL APIs mean you can connect Supabase directly to your no-code frontend without spinning up a custom backend.

It's open-source, so you're never locked into a vendor, and the free tier is generous enough to explore before scaling. No-code builders like Bubble, FlutterFlow, and Adalo integrate cleanly with Postgres backends, and Supabase offers the auth and file storage most apps need out of the box.