It's just the firebase library that is itself too big.
If someone wrote a more sensible library for Espruino that interfaced to that then it should only take a few kb, and I'd be happy to host it on the Espruino site.
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
Just to add, it'll be pretty easy to use firebase on any Espruino board that supports HTTPS using their REST API: https://firebase.google.com/docs/referenĀce/rest/database/
It's just the firebase library that is itself too big.
If someone wrote a more sensible library for Espruino that interfaced to that then it should only take a few kb, and I'd be happy to host it on the Espruino site.