Not sure friendfeed ever got enough users to know scaling issues...
Personally I would go with async DB, or have DB access in its own thread(s) and async communicate with that.
Personally I would go with async DB, or have DB access in its own thread(s) and async communicate with that.
I figure after the first million users, your embarrassingly parellel app server layer is not your bottleneck, it's getting the database to scale.