How to correctly implement the task (description below)?

Question

iOS

I don't know if you've experienced a similar problem, but I'll ask. Question on the technical side.
We are making an application like “YouTube”. One video can be stored in all servers (there are 3 of them - A, B, C).
For authorization and server addresses, we store in FireBase.
Here's what we want to implement...
When more than 50 users have connected to server A, the next one is connected to server B.
Servers are chosen not by users, but by the application.
How to implement it? Competently and qualitatively?)
We use FireBase. Does he have such opportunities? And if not, how can we implement it? How to get data that a particular user is already connected, for example; from 3 devices and how many connections to the server do we currently have...?
Thank you!

Answer 1

Everything that you described should be done by the backend and return to the client the URL on which he should already go and show the vidos.