CDN Content Distribution & Caching 3

Question 1

Which CDN feature allows different versions of the same URL to be cached based on the user's geographic location?

Accepted Answer

Vary-based caching with geographic keys

Answer

Adding geographic identifiers to the cache key enables distinct cached responses per region for the same URL.

Question 2

What is the primary risk of setting excessively long TTLs (e.g., 1 year) for HTML pages on a CDN?

Accepted Answer

Stale content being served after site updates

Answer

Long TTLs mean updated HTML may not reach users until caches expire, requiring manual purges for timely updates.

Question 3

A CDN uses 'request coalescing' (also called request collapsing). What problem does this solve?

Accepted Answer

Prevents multiple simultaneous cache misses from all hitting origin for the same resource

Answer

Request coalescing queues duplicate in-flight requests at the edge so only one request goes to origin, preventing thundering herd.

Question 4

Which metric specifically measures the percentage of requests served from CDN cache without hitting origin?

Accepted Answer

Cache hit ratio (CHR)

Answer

Cache hit ratio is the fraction of total requests served from cache, directly measuring CDN caching effectiveness.

Question 5

Edge Side Includes (ESI) are primarily used to:

Accepted Answer

Assemble web pages from individually cacheable fragments at the edge

Answer

ESI allows edge servers to stitch together page fragments with different cache lifetimes, enabling partial page caching.

(CDN) Content Delivery Network Certification Practice Test