Edge cache vs. browser cache: a Seoul app tunes two layers

Edge cache vs. browser cache: a Seoul app tunes two layers
A productivity web app set a 1-year immutable cache on its hashed JS bundles — correct for browser caching. But it set the same long TTL on its API responses at the edge, and users in Seoul saw stale notification counts for hours.
Support tickets about 'wrong unread badge' climbed to 60 a week.
They split the layers deliberately: immutable browser cache for fingerprinted static assets (the browser never re-asks), and a short 30-second edge cache with revalidation for API data (shared across users, but fresh).
Static asset requests to the edge fell 80% on repeat visits. Stale-badge tickets dropped to near zero.
Browser cache wins for per-user, versioned assets. Edge cache wins for shared, semi-dynamic data many users request at once.
The number that mattered: stale-badge tickets from 60/week to nearly zero.