The Tail at Scale: Concepts, Techniques and Impact
The Tail at Scale is a foundational paper that introduced a critical problem in large-scale distributed systems and proposed a new way to solve it. It’s important because it was among the first to clearly define and articulate tail latency , the issue of outlier requests taking significantly longer to complete. It identified the many causes of this variability and presented solutions that were not just theoretical but had been deployed at Google and are now standard in the industry. Tail latency refers to the latency experienced by the slowest requests in a distributed system, typically measured at the 99th percentile (p99) or higher. While a system may have an excellent average latency, the slowest requests can cause a poor user experience. The paper introduces the concept of a tail-tolerant system, drawing an analogy to a fault-tolerant system. A fault-tolerant system is designed to handle hardware failures, while a tail-tolerant system is designed to handle the temporary latenc...