Q: Can Firebase be used in an app supported by another Backend and Database? I am looking to make an app that would have its Backend on another service like AWS or some other. This app would be having many features and functionalities.
But for chat feature, I am exploring options and wondering that would I be able to integrate Firebase in my app.
I have read about Firebase Functions to add more functionality at the backend and also the installation of Firebase Admin to servers.
But still I am not convinced about their capabilities and exactly what all I can do with them.
It would be great if someone who has experience with Firebase help me out figuring if going with it is the best case for me or is there something else I should look into.

A: So first you can't use Firebase in combination with AWS or Azure etc. Firebase is based on Google Cloud and is the interface between the mobile client (the running app on the client's smartphone) and the backend (your Firebase project).
What I use is, for example, Firebase Cloud Messaging, to simply notify one or multiple users by trigger an HTTP Request from my own web server. 
I also made some apps to store the data in FireStore or in the Realtime-Database, so that I don't have to set up a whole new infrastructure. And this is basically the goal of Firebase that you can simply start with your app, without carrying about that.
So what I've heard about Firebase is that you currently cannot install Firebase on a server of your choice and you have to use Google Cloud.
Hopefully, you can do something with my answer. If you have further questions feel free to ask them.
