Myth: purging the cache guarantees users see fresh content

Myth: purging the cache guarantees users see fresh content
This week in caching, the purge illusion:
— The belief: hit purge, everyone gets the new version.
— Reality: you only purged the layer you clicked. Browser cache, intermediate proxies, and edge nodes you didn't target still hold the old copy until their own TTL lapses or they're explicitly invalidated.
— Worth your time: trace a request end to end after a purge and read every Age and Cache-Control header in the chain. Purge is per-store, not global.
Bookmark: there is no single purge button for the internet. Version your URLs/assets so a 'purge' is really a swap to a new key nobody has cached yet.