I have a game being mostly used by kids and it doesn't generate revenue, and it has been in the free tier of Firebase for about 2 years. This month suddenly my account got disabled due to DB usage (I only keep sessions and ids, still can't believe I exceeded DB usage). But the traffic was same as old. About 1.5 weeks ago I woke up at 6am with an e-mail telling me my account was disabled. And I had to switch to something else, spending hours. I don't recommend using Firebase to anyone anymore.