Points of presence
A point of presence, or PoP, is a physical site where a CDN runs edge servers, often inside an internet exchange near many users. Each PoP holds caches and terminates user connections.
The fill path
When a user requests content the PoP does not have, that is a cache miss. The PoP fetches the object from the origin, stores it, and returns it. Later users for the same object get a fast cache hit from the PoP.
Roles split cleanly
- Origin owns the authoritative content and rarely changes.
- PoP holds short lived copies and serves nearby users.
- Cache rules decide how long a PoP keeps each object.
Why this layering helps
Most reads are served at the edge, so the origin sees only the first miss per object per PoP. This keeps origin load low and lets you place heavy origin infrastructure in just a few regions.
Key idea
A PoP serves nearby users from cache and fills from the origin only on a miss, so the origin handles a tiny fraction of total reads.