caching – Page 4 – Türker Yıldırım

The REST response we cached at the edge

NoteJanuary 20, 20232 min read

A public REST endpoint serving the same payload to everybody, hit forty thousand times a day, and generated forty thousand times. WordPress sends no-cache on REST responses by…

WeakMap for a cache that must not keep objects alive

NoteJanuary 18, 20232 min read

A per-request memoisation cache keyed by object was holding every entity loaded during a long-running command, and the command was using 900 MB by the end. This only…

A cache invalidation bug that only appeared under load

Deep diveOctober 17, 202210 min read

Correct in every test, wrong for about one request in four thousand. A read that races a write, and a cache that keeps the loser.

wp_cache_get without a persistent backend is a request cache

NoteOctober 13, 20222 min read

The object cache API is always available and, without a drop-in, discards everything at the end of the request. Within a request it is still worth having —…

Web fonts that stopped blocking the render

Deep diveSeptember 28, 202210 min read

600ms of the largest contentful paint was a font file. font-display: block, and a page that renders in stages.

A read-through cache that stampedes exactly once

Deep diveAugust 24, 202210 min read

A cache entry expired at 09:00 and four hundred requests recomputed it. A latency spike every hour, exactly on the hour.

ETags give you optimistic concurrency for free

NoteJuly 28, 20222 min read

The read side saves a response body when clients cooperate; the write side prevents a lost update whether they cooperate or not. Making If-Match mandatory rather than optional…

Sessions in Redis, and the logout that did not

Deep diveJune 29, 202210 min read

A session store move that changed the security properties. Logging out on one device leaves the others signed in.

Sticky reads after a write, and the window they cover

NoteMay 24, 20222 min read

Routing reads to a replica is correct except immediately after a write by the same user, and the usual fix is a time window rather than a guarantee.…

Probabilistic early expiration avoids the lock entirely

NoteMay 19, 20222 min read

A cache entry expiring under load means every concurrent request recomputes it, and a lock makes them queue instead. One request recomputes slightly early while everybody else is…