Push messaging/events

What are people using for push messaging/events?
I don’t mean push notifications. I’m talking more about the kind of functionality you get from firebase’s cloud messaging (which isn’t supported by expo unfortunately) or google cloud messaging or AWS SNS.

The use case i’m looking to explore is how the app can be subscribed to certain events and when they happen for it to execute some logic (like updating local state, scheduling a local notificaton, etc)

The only way i see this happening right now is by leveraging firebase database as a sort of messaging queue.