Im programming on a turn based war-game for some years now (along with the engine) and Im having quite a hard time at figuring out what the games server architecture should look like, since most game server architecture articles I found focus either on FPS oder MMOGs, which doesn't really fit since I want many matches with 1- 16 players on my server, with each match being played in turn based mode.

My chief concern is memory usage, since the most basic approach of loading every game that is being played completely into RAM should be quite inefficient, so is there a suitable strategy for selecting only the needed bits and loading them?

Another question I got is how to design the threading on the server, since I think using only a single thread could be a problem due to the fact that the game or part of it might have to be loaded from the database.

I would be very happy if you could share your knowledge or point me to material on this topic.