Regional vs. global cache key: a Jakarta marketplace fixes price chaos

Regional vs. global cache key: a Jakarta marketplace fixes price chaos
A marketplace showed prices in local currency, set per region at origin. Their cache key was global, so whichever region warmed a product page first won — and a buyer in Jakarta sometimes saw euros, while a Berlin user saw rupiah.
Mispriced page views ran 4% of traffic, and support drowned.
They added the CDN's region code into the cache key, so each currency variant cached separately per region.
Currency-mismatch reports fell to zero. Hit ratio dipped only 3 points because most regions still reused their own warm copy heavily.
Global keys win when content is truly identical worldwide — maximize reuse. Regional keys win the moment a response legitimately differs by geography and a wrong variant is a real error.
The number that mattered: currency mismatches from 4% of views to zero.