Abstract

Edge caching moves content closer to users by storing responses at geographically distributed nodes, reducing origin load and cutting latency. This post covers three practical strategies for getting the most out of your CDN layer.

Cache-Control Tuning

Setting aggressive max-age values on static assets while using stale-while-revalidate for semi-dynamic content lets clients serve stale responses immediately while the CDN revalidates in the background. This eliminates the “thundering herd” problem on popular pages.

Surrogate Keys

Tag responses with surrogate keys (Fastly calls them “cache tags”; Cloudflare uses “Cache-Tag” headers) to purge entire logical groups, all pages for a product SKU for example, with a single API call rather than URL-by-URL invalidation.

Edge-Side Personalization

Vary caching on a thin session token rather than full cookies. Cache the page shell at the edge and fetch only the personalized fragment from origin, keeping hit rates high without serving wrong content to the wrong user.