1. A method of routing requests within a system having a plurality of server pools, the method comprising: receiving a request at the system; first determining a first value associated with a first request type of the received request, the first value modeling a number of requests of the first request type in a virtual queue; second determining probabilities of routing based on the first value and probabilities of rerouting for further processing, the second determining being performed without determining an input rate of received requests of the first request type; and routing the received request to at least one of the plurality of server pools based on the probabilities of routing.