I'm so excited for Supabase. As soon as they move Realtime Subscriptions out of alpha / beta, I will replace Firebase on all new projects. The Firebase / Firestore analog - Snapshot Listeners - give your application a real-time backend for free and simplifies state management drastically since your subscriptions are your store.

Supabase being built on SQL is interesting to me- I love PSQL and the row-level security rules are incredible. But the historical SQL v NoSQL debate involves the trade-offs of Consistency, Availability, and Partition Tolerance [0]. With Firebase (and typically NoSQL) you lose Consistency and you get a bit of redundance by virtue of using onWrite listeners as opposed to Joins. That model scales really well since it's amenable to sharding seamlessly. What will scaling a Supabase backend look like?

[0] https://www.bmc.com/blogs/cap-theorem/