CDN Architecture & Components 3

Question 1

What is the function of a CDN 'manifest file' in adaptive bitrate (ABR) streaming?

Accepted Answer

It describes available video renditions and their segment URLs for the player

Answer

A manifest (e.g., HLS .m3u8 or DASH .mpd) enumerates each quality rendition and segment location so the player can switch bitrates dynamically.

Question 2

Which CDN architectural pattern uses geographically distributed 'scrubbing centers' to absorb volumetric DDoS traffic before it reaches PoPs?

Accepted Answer

DDoS mitigation via traffic scrubbing

Answer

Scrubbing centers inspect and filter attack traffic in-line, passing only clean traffic onward to the CDN edge nodes.

Question 3

In CDN architecture, what is a 'cache key' and why does it matter?

Accepted Answer

The unique identifier (typically URL + selected headers) used to look up a cached object

Answer

The cache key determines cache hit/miss logic; including the wrong headers (e.g., User-Agent) can fragment the cache and reduce hit rates.

Question 4

What is 'stale-while-revalidate' behavior in a CDN cache?

Accepted Answer

The CDN serves a stale cached object immediately while asynchronously fetching a fresh copy

Answer

Stale-while-revalidate lets the CDN serve the old cached version instantly, then refresh it in the background, eliminating user-perceived latency.

Question 5

Which component in a CDN stack typically handles real-time log streaming and analytics aggregation across all edge nodes?

Accepted Answer

Log aggregation pipeline (e.g., Kafka + ClickHouse)

Answer

High-volume edge logs are streamed via message queues and stored in columnar databases to support real-time analytics dashboards.

(CDN) Content Delivery Network Certification Practice Test