Cache Stampede

Your cache is working perfectly. Hit rates are above 95%, latency is consistently low, and your database is humming along at a comfortable load.

Then a single popular cache entry expires, and within milliseconds, your database is drowning in thousands of identical queries. Response times spike. Timeouts cascade. Users start seeing errors.

This is a cache stampede, also known as the thundering herd problem. It happens when many requests simultaneously try to rebuild the same cache entry, overwhelming your database with redundant work.

The irony is that caching is supposed to protect your database, but a stampede turns the cache into a weapon against it.

In this chapter, we will explore: