Cache Stampede

A cache protects a database by absorbing repeated reads.

But when a popular cached value disappears, many requests can miss at the same time. If every request tries to rebuild the value independently, the database receives a burst of duplicate work.

That is a cache stampede, also called the thundering herd problem.

What makes this dangerous is the volume of concurrent misses landing on the same key, all racing to rebuild it.

In this chapter, we will cover what a cache stampede is, why stampedes happen, how they affect a system, the main prevention strategies, how to monitor and detect them, and the production practices that reduce the risk.