Firebase is a great choice for realtime data stuff. No more polling GET calls. The docs are good but their YouTube tutorials are better and get you started in less time. If you use some other Google infrastructure pieces this will be right there in the same place rather than keeping track of another platform.
We love Firebase! It is an amazing platform for fast applications providing a consistent development experience across many products.
We have used other platforms that have very disconnected services but firebase wraps it all up in a nice package!
I've been a fan of Firebase ever since before they were acquired by Google. I don't know of any other platform that has the same functionality of synchronous key-value mapping between client connections.