I'm missing something.
When a user registe on Firebase for notifications, it sends to my server its ID that I store in a map. When an event occour on the server I need to send notifications to some ID.
I'll never know if the user uninstall the app, so I will forever send notifications to that user. Ok, Firebase will discard it. Ok, it is not much traffic.
But I'm thinking if it is better to implement something that purges users after some time that they do not refresh their subscriptions.
Or Firebase can reply me that an user does no longer exists when I try to send him a notification ?