What's the best server architecture for real-time games?

I'm developing a Real-Time game which should hold thousands of players in real-time (FPS like. max 1s lag). What would be the best infrastructure for this?

My idea was using 2 server clusters - one for the Server End (all the computing side) and one for the Database end, where a load balancer is "responsible" for each of the clusters. One main server will receive the requests from the users and send back the IP address of the relevant server that the user can work this.

The database cluster will use database replication for consistency between the databases.

There should be a geographical load balancer as well - so it will assign the regional load balancer to each user for best response.

I'm using .NET + MSSQL for the game.

Thanks!