What is the primary function of a CDN cache?

What is the primary function of a CDN cache?

• A. Caches dynamic content at the origin server.
• B. Stores data in a centralized cache for global access.
• C. Caches application data in the server's local memory only.
• D. A geographically distributed network of edge servers that cache content close to users, eliminating round trips to the origin server.

Answer: (D)

The main idea being tested is that a CDN cache brings content closer to users by using a distributed network of edge servers to store copies of assets. This means when someone requests a file, the CDN serves it from an edge server near them, rather than always reaching back to the origin. If the content is already cached at the edge (a cache hit), the response is fast and avoids extra network hops. If it isn’t cached yet (a cache miss), the edge node fetches it from the origin, stores a copy, and serves it, so future requests can be served locally. This setup reduces latency, lowers bandwidth load on the origin, and improves scalability and resilience, especially for global traffic. The other options describe scenarios that don’t reflect the distributed edge-caching model: caching only at the origin, using a centralized cache, or keeping data only in a single server’s local memory. Those don’t capture how a CDN operates across many edge locations to bring content closer to users.

The main idea being tested is that a CDN cache brings content closer to users by using a distributed network of edge servers to store copies of assets. This means when someone requests a file, the CDN serves it from an edge server near them, rather than always reaching back to the origin. If the content is already cached at the edge (a cache hit), the response is fast and avoids extra network hops. If it isn’t cached yet (a cache miss), the edge node fetches it from the origin, stores a copy, and serves it, so future requests can be served locally. This setup reduces latency, lowers bandwidth load on the origin, and improves scalability and resilience, especially for global traffic.

The other options describe scenarios that don’t reflect the distributed edge-caching model: caching only at the origin, using a centralized cache, or keeping data only in a single server’s local memory. Those don’t capture how a CDN operates across many edge locations to bring content closer to users.