Thundering herd
Many clients or processes wake up and act at the same moment, for example after a restart, a cache expiry, or a shared timer, and their combined load overwhelms a shared resource. The fixes spread the herd out: jitter, request coalescing, and staggered restarts.
Reliability
In Quorum#
The Cache stampede Incident restarts a Cache empty, and every miss goes to the Database at once; while the Database runs at 90% or more, refills time out and the Cache stays cold. Stampede protection lets a cold Cache send on only 25% of its extra misses while the rest wait on one fetch, and Cache warming brings a Cache back 80% warm. Naive retries are a herd too: every caller retries at once, and Backoff with jitter spreads them out.
Read next#
Cache stampede, Retry with backoff and jitter, Cache warming, Metastable failure