Edge Cache and CDN Platform · View 09 of 29 · 3 · Structure
The order is the design
- The signed URL is verified and stripped before the property is resolved. The token never reaches the key, so a million signed URLs for one object remain one cached object.
- The request resolves to exactly one property and one rule, or it is refused with 421. A request that matches nothing is never passed through to a guessed origin.
- The tag table is checked after the key is built and before the stored object is served. An object stored before its tag was invalidated is treated as a miss or as stale, depending on the rule's mode.
On a miss
- A local miss goes first to the node that owns the key on the PoP's ring, then to the shield. The PoP behaves like one cache six times the size of a node, at the cost of one hop over the local fabric (ADR-07).
- An object that fails its checksum on read is evicted and treated as a miss. It is never served.
Numbers
- Loopback hop between Envoy and Traffic Server under 0.2 ms at p99; intra-PoP owner hop under 1 ms.
- Objects above 8 MB are cached in slices, so the first byte of a 4 GB file is served without the whole file being present.
