Caches are supposed to protect your backend from load. Most of the time they do. But there is a specific failure mode where the cache itself becomes the trigger for an outage: the cache stampede, also known as the thundering herd problem. It shows up in systems that otherwise look healthy, which is what makes it so disruptive when it finally happens. What a Cache Stampede Is A cache stampede happens when a single cached value, one that many requests depend on, expires or gets evi...