If you are looking for an open-source replacement of the Firebase Realtime Database, you might also be interested in Icepeak (https://github.com/channable/icepeak) (full disclosure, I'm one of the authors).
Icepeak was written because we were unsatisfied with the reliability and with the (occasionally) high latency of Firebase, both for pushing updates via HTTP (>1s for some requests) and for receiving updates over websockets.
This was about 3 years ago though, so I hope that Google improved the quality of the service in the mean time.
Icepeak was written because we were unsatisfied with the reliability and with the (occasionally) high latency of Firebase, both for pushing updates via HTTP (>1s for some requests) and for receiving updates over websockets.
This was about 3 years ago though, so I hope that Google improved the quality of the service in the mean time.