cache stampede

RU: cache stampede (давка на кеше)

A failure pattern where a popular cache entry expires and many concurrent requests simultaneously miss and each tries to regenerate it, overwhelming the origin. Also called thundering herd. Mitigations include request coalescing (singleflight), locking the rebuild to one requester, and probabilistic early expiration (XFetch), which refreshes a key slightly before its TTL with increasing probability.