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Origin shield

A CDN layer between the edges and the origin, so many edges missing the same file cost the origin one fetch.

Taught in Chapter 15: The Edge.

More from the same chapter

• Cache key: What a cache files each copy under, usually the URL.
• CDN: A content delivery network: caches in cities around the world, close to users.
• Edge and origin: The edge is a CDN location near users; the origin is your own servers behind it.
• Purge: Removing a CDN's cached copy before its TTL runs out, usually after the content changed. It takes from a fraction of a second to minutes to reach every edge, depending on the CDN.
• Static and dynamic content: Static content is the same for everyone and caches well; dynamic content is built per user.