Firebase authentication limit login by the same user

Question

is there a way in Firebase to limit the number of logins by the same user at the same time, says I want to put a limit of 3 devices at a time for one single account, how can

Answer 1

That is not supported by Firebase. The best you can do is keep track of the token auth_time. This is the time of sign-in. You would keep a queue of 3 entries for that. Each time you sign-in a user, send their ID token for verification, add the auth_time to the queue (if it is not there already) and dequeue the oldest auth_time in the queue if it exceeds it maximum size (3) . You would only allow access to data for ID tokens with auth_times within that queue.