Cache stampede
When a popular cache key expires and many concurrent requests miss simultaneously.
Origin
The pathology has been around as long as caches; the name and mitigations (probabilistic early expiration, request coalescing, lock-on-miss) were formalised in writeups from Instagram, Memcache, and Stack Overflow in the early 2010s.
Where it shows up in production
- Instagram — thundering herd Engineering blog walks through promise-based coalescing in their feed cache.
- Memcached GET hits with no value can serialise behind one fetch via the `add` lock trick.
On Semicolony
Sources & further reading
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