Latency: How quickly are transactions supposed to return success or failure? Users seem to be ok with a flight search or a credit card transaction taking their time. A web search has to return within a few hundred milliseconds. A widget or API that outside systems depend on should return in 100 milliseconds or less. More important is to maintain application latency within a narrow band. It is worse to answer 90% of queries in 0.1 seconds and the rest in 2 seconds, rather than all requests in 0.2 seconds.
