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SPECIFICATION · CONCEPT BRIEFDWG · 14-CACHE-THE-WORLD

Cache the World

Most read traffic should never reach your origin. That's what edges are for.

§01Why an edge cache

Read-heavy traffic — product pages, images, JS bundles, news articles — is mostly the same answer over and over. Asking your origin server for it every time wastes capacity you'll need for the unique requests (checkouts, personalised feeds, writes).

A CDN sits between your client and your origin. On a hit, it answers immediately and never calls back. On a miss, it forwards to the origin and caches the answer for next time.

§02Hit rate is everything

  • If 90% of traffic hits the CDN, your origin only sees 10% — capacity multiplied by 10×.
  • Cacheable content is anything safe to share between users (with the right keying).
  • Cache invalidation is the hard part — short TTLs are usually fine for v1.
⚑ NOTE
This level
The origin server's capacity is well below the incoming traffic. Without a CDN, drops mount. Insert a CDN between client and server with a high hit rate and watch the origin breathe.
⚑ CHEATSHEET · QUICK REFERENCE
  • Put a CDN in front of any read-heavy, cache-friendly endpoint.
  • The CDN's hit rate is your origin offload multiplier. 90% hit ⇒ 10× the headroom.
▸ THE EXERCISE

Read-heavy traffic is overwhelming a single origin server. Insert a CDN between client and origin so most reads terminate at the edge and never reach your backend.

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