If you define throughput as "processed items over time per processor", the tradeoff becomes clear. Given the rate of incoming requests, you can get more process

If you define throughput as "processed items over time per processor", the tradeoff becomes clear. Given the rate of incoming requests, you can get more processors, which will increase cost and reduce latency and throughput-per-processor, or you can get fewer processors, which will decrease cost and increase latency and throughput-per-processor. If you have fixed resources and fixed work, wanting your queues to be empty is a wish, not a strategy.