Studying latency behavior can tell us a lot about a system. It can help us focus our efforts on the parts that matter most for keeping systems reactive and responsive. It can save us time and lead to better systems. But it is an often overlooked part of system modeling, development, testing, and monitoring efforts.

In this talk, Gil Tene discusses various characteristic behavior patterns of latency behavior, and shows what we can learn about systems by simply observing their latency behavior in detail, and in the context that matters to the system at hand. The latency involved in "from stand-still" reaction to a single event is different from the latency involved in processing a message coming off of a hot stream. The latency behavior experienced when waiting in line in a queue is different from the one seen when traversing a constant length operation or physical distance. We'll discuss the implications of these and other characteristics on the way system behave in the real world, and on the information we need to gather when testing systems in order to understand their reaction and responsiveness.