What is a CDN PoP (point of presence)?
A PoP is a CDN data center that terminates visitor connections and holds its own cache. A page cached in one PoP is not cached in the others.
A PoP, or point of presence, is a data center where a CDN terminates visitor connections and serves content. Each PoP has its own cache. Visitors are routed to a PoP close to them, so a page cached in one PoP can still be a miss for visitors who reach a different one.
visitor (Madrid) -> PoP MAD -> miss -> upper tier or origin
visitor (Madrid) -> PoP MAD -> hitCDNs do not copy every object to every PoP. A PoP fills its cache on demand, from the requests it receives, and evicts objects that are not requested. A purge clears an object from all of them at once.
- Tiered caching lets PoPs fetch from an upper tier instead of each going to the origin.
- Warming has to happen where visitors are. A request from one region fills that region's PoP, not the others, which is why cache warming uses several vantage points.
Related terms
References
- Cloudflare: Tiered Cachehttps://developers.cloudflare.com/cache/how-to/tiered-cache/
- Fastly: Shieldinghttps://www.fastly.com/documentation/guides/concepts/shielding/
- MDN: HTTP cachinghttps://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching
Warm your cache after every deploy
sitewarm requests the pages in your sitemap after a deploy and reports the cache state the CDN returns for each one, with the vantage point it was measured from.