CDN CDN Origin Shield & Pull/Push Zones 1 — Questions and Answers
Question 1: What is the primary purpose of an origin shield in a CDN architecture?
- To encrypt traffic between edge nodes
- To act as a mid-tier cache that reduces the number of requests reaching the origin server (Correct answer)
- To load-balance between multiple CDN providers
- To generate dynamic content at the edge
Correct 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.
Question 2: Which scenario benefits most from enabling origin shield?
- A site with 100% dynamic, personalized content
- A high-traffic media site with large cacheable assets and a single origin data center (Correct answer)
- A real-time WebSocket application
- A site already using a multi-region origin setup
Correct 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.
Question 3: What is a 'pull zone' in CDN terminology?
- A zone where CDN pushes files to edge nodes proactively
- A CDN configuration where edge nodes fetch content from the origin on demand when a cache miss occurs (Correct answer)
- A geographic region restricted from accessing content
- A billing zone for egress traffic
Correct 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.
Question 4: What is a 'push zone' in CDN terminology?
- A zone that pushes cached content invalidations to users
- A storage zone where operators proactively upload files directly to CDN edge storage for immediate availability (Correct answer)
- An automated origin health-push mechanism
- A DNS push notification system
Correct 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.
Question 5: When using origin shield, which cache TTL setting has the most impact on reducing origin requests?
- Browser cache TTL
- Shield-to-edge TTL
- Origin cache-control max-age (Correct answer)
- DNS TTL
Correct 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.
Question 6: What is 'cache coalescing' (also called request collapsing) at an origin shield node?
- Merging multiple CDN providers into one
- Queuing concurrent cache-miss requests for the same object and sending only one upstream request to the origin (Correct answer)
- Combining small files into a single larger cached object
- Merging TTL values from multiple Cache-Control headers
Correct 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.
CDN CDN Origin Shield & Pull/Push Zones 1
What is the primary purpose of an origin shield in a CDN architecture?