i just built a system like this w/Erlang. we have 'post office boxes' that can receive messages, each is unique, one per connected client, and certain 'PO boxes' can subscribe to others', if they want, or to a random sampling of general message from a group of other boxes. Erlang is perfect for this. We've projected that we will max out at around 1MM connections on a 48GB, 8 core box. We're running 150K connections right now and it's using about 17% of memory and much less CPU. The key though is we already tested with multiple boxes and it works the same way. There's no refactoring when we run out of space on one box. Email me if you want some other ideas about how to set this up in Erlang.