Passenger spawns copies of your application and (I think this is the default now, it wasn't before) puts your requests in a queue, so that as the app instances

Passenger spawns copies of your application and (I think this is the default now, it wasn't before) puts your requests in a queue, so that as the app instances finish processing requests they snatch a new request off the queue. If they are all busy then the requests back up on the queue until one of them becomes available.