“At a high level, this workload is simultaneously latency-sensitive and throughput-bound. Each web server needs to respond to a given user request quickly as well as serve requests from multiple users in parallel. In CPU terms, we require good single-thread performance and excellent throughput with a large number of concurrent threads. We have architected this workload so that we can parallelize the requests using PHP's stateless execution model. There isn't much interaction between requests on a given web server, allowing us to efficiently scale out across a large number of machines.”