A common pattern is to have a server process running that watches parts of the firebase tree and then runs business logic in response to changes. It's describe

A common pattern is to have a server process running that watches parts of the firebase tree and then runs business logic in response to changes. It's described as client - db - server rather than client - server - db. I believe there are also Firebase queue and task abstractions that make it fairly easy to map a write to a 'backend handler'.