CDN Origin Shield & Pull/Push Zones Flashcards

What is the primary purpose of an origin shield in a CDN architecture?

Answer: To act as a mid-tier cache that reduces the number of requests reaching the origin server

An origin shield is a designated CDN node that consolidates cache misses from all edge PoPs, dramatically reducing origin load by serving as a single cache layer above the origin.

Which scenario benefits most from enabling origin shield?

Answer: A high-traffic media site with large cacheable assets and a single origin data center

Origin shield delivers maximum benefit when content is cacheable and the origin has limited capacity, as it collapses many edge cache misses into a single origin request.

What is a 'pull zone' in CDN terminology?

Answer: A CDN configuration where edge nodes fetch content from the origin on demand when a cache miss occurs

A pull zone lazily fetches content from the origin on first request and caches it at the edge, requiring no pre-upload of assets by the operator.

What is a 'push zone' in CDN terminology?

Answer: A storage zone where operators proactively upload files directly to CDN edge storage for immediate availability

A push zone allows operators to upload files directly to CDN edge storage via API or FTP/SFTP, ensuring content is available before any user requests it.

When using origin shield, which cache TTL setting has the most impact on reducing origin requests?

Answer: Origin cache-control max-age

The origin's Cache-Control max-age determines how long the shield node retains content before re-fetching from origin, directly controlling origin request frequency.

What is 'cache coalescing' (also called request collapsing) at an origin shield node?

Answer: Queuing concurrent cache-miss requests for the same object and sending only one upstream request to the origin

Request collapsing holds duplicate in-flight cache-miss requests at the shield and fulfills them all with a single origin fetch, preventing thundering herd on popular content.