In Taming The Long Latency Tail we covered Luiz Barroso’s exploration of the long tail latency (some operations are really slow) problems generated by large fanout architectures (a request is composed of potentially thousands of other requests). You may have noticed there weren’t a lot of solutions. That’s where a talk I attended, Achieving Rapid Response Times in Large Online Services (slide deck), by Jeff Dean, also of Google, comes in:

In this talk, I’ll describe a collection of techniques and practices lowering response times in large distributed systems whose components run on shared clusters of machines, where pieces of these systems are subject to interference by other tasks, and where unpredictable latency hiccups are the norm, not the exception.

The goal is to use software techniques to reduce variability given the increasing variability in underlying hardware, the need to handle dynamic workloads on a shared infrastructure, and the need to use large fanout architectures to operate at scale.

Two forces motivate Google’s work on latency tolerance: