Some time ago I wrote server software which is currently running at it's max. (3k users average). So I decided to rewrite certain parts so I can run the software at another server to balance it's load.

I can't simply start another instance of the server since there is some data which has to be available to all users. So I was thinking of creating a small manager and all the servers connect and send their (relevant)data to the manager.

But it also got me thinking about another problem. The manager could also reach it's limits which is exactly what i'm trying to prevent in the future.

So I would like to know how I could fix this problem.

(I have already tried to optimize critical parts of the software but I can't optimize it forever)