[RaphiePS]

I guess it all depends on how "deeply" realtime your app needs to be.

For example, if you just want to add chat between users I think you'd be well-served by Firebase for the chat. If you want to roll-your-own, there are a million Node.js chat tutorials.

However, if you'll be making important changes to "real" data, as in anything you're persisting with ActiveRecord, b is your best bet.