Can the server know which message topics have subscribers?

Question

Is there a way for a server application that sends topic messages through FCM to find out which topics actually have subscribers?

We have a potentially large number of topics, and we would like to avoid the need to always send messages to all of them, since only a subset will be active at any given time. I know that a server can request certain topics with an InstanceID subscription, but repeating over a thousand of them sounds like a bad idea.

We can overturn our own solution, but since this information already exists in Firebase, it would be desirable to simply get it from there.

Answer 1

No. There is currently no way to request the number of subscribers per topic, you will need to maintain a connection between the token and the themes on your application server.