Nicholas Allen’s Indigo Blog : Queue Scalability

A quick way to judge which way you need to scale next with your queue is to look at the bottlenecked resource. If you have exhausted the amount of network bandwidth you have moving messages out of the queue, then you should be thinking about moving the queues close to the service and scaling up. If you have exhausted the amount of computational power, either processing or disk, then you should be thinking about replicating the service to scale out and read from a remote queue. If clients are having trouble but you’ve maxed out neither your network nor computational power, then you probably need to go back and fix your quotas.