One idea I liked was ... You have an authoritive world simulation server, as usual. You then have several servers whose chief job is to keep clients in sync w

One idea I liked was ... You have an authoritive world simulation server, as usual. You then have several servers whose chief job is to keep clients in sync with the authoritive server. Most network games combine these two roles, but there is a lot of processing and network traffic required to keep clients in sync. For massive multiplayer there is a benefit to scale the "client-interaction" servers.