The below page from firebase mentions that an App instance can not be part of more than 2K FCM topics.

https://firebase.google.com/docs/cloud-messaging/android/topic-messaging

One app instance can be subscribed to no more than 2000 topics.

I have seen related questions and answers. But I still have some doubts.

Let's say, my Flutter-based App XYZ has 50K users. And in a hypothetical scenario, each user has subscribed to one unique topic i.e. 50K topics across users.

Will I be still able to use Firebase FCM for all the 50K topics?

Please help with the clarification.

CodePudding user response：

The limit is not on the number of topics that can exists, but the number of topics that a single app instance can subscribe to. A single app instance can subscribe to at most 2,000 topics, but there's no such limit across app instances.

So if each of your 50K users has a single app instance, they could subscribe to 50,000 * 20,000 topics.