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CDN Caching Deep Dive: Edge, Vary, and Purge

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CDN caches are shared: different rules apply

A browser cache serves one user. A CDN edge cache serves all users in a region — potentially millions of requests per second from the same cached object. This shared nature requires different directives and more powerful invalidation tools.

s-maxage sets CDN TTL independently of browser TTL. Surrogate keys let you invalidate thousands of cached pages when one product updates. stale-while-revalidate serves instantly while refreshing silently.

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