TL;DR; We had performance spikes, which we eased with some insane use of structs. History For a while now, we had been seeing a problem in the Stack Exchange engine where we would see regular and predictable stalls in performance. So much so that our sysadmins blogged about it back here. Annoyingly, we could only see this problem from the outside (i.e. haproxy logging, etc) – and to cut a very lon