Edge cache
Physical POP close to users. First hop. Cache hit = 10-50ms. Miss = ask upstream.
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Edge cache
Physical POP close to users. First hop. Cache hit = 10-50ms. Miss = ask upstream.
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Regional cache
Aggregates edges. Reduces load on origin. Regional cache miss for content already at another edge = origin load.
Cache-Control drives it
Cache-Control: public, max-age=3600. Edge honors. Immutable assets get max-age=1 year.
Cache invalidation
Deploy new asset → old cache still serves. Solutions: content-hashed filenames (immutable) OR purge API (slow, expensive).
Dynamic content
Personalized responses can't be cached. CDN edge terminates TLS + proxies to origin. Still wins on TLS handshake savings.