L12
CDN compared with a load balancer
Cram this first — memory hook
Content Delivery Network = copies closer; load balancer = distribute back-end work.
Exam trap
A is not just another name for an active-passive server cluster.
The slide facts
No dedicated Content Delivery Network lesson was located in the seven supplied decks. This topic remains included because it is explicitly in your scope; the explanation below is additional teaching.
If you have time — extra
A Content Delivery Network () uses geographically distributed edge locations to serve eligible content closer to users. Imagine keeping copies of a popular textbook at several local libraries instead of sending every borrower to one central library. A cache hit can be served from an edge; a cache miss may require the origin server. Content expires or is refreshed according to caching rules. Personalized and sensitive data require careful policies and must not be casually cached for everyone. A load balancer primarily distributes requests among back-end resources, while a reduces distance and origin demand for suitable content. They can coexist. A can offer other services too, but caching every application response is not automatic.
Walkthrough
The user requests an image. A suitable edge handles the request. If a valid cached copy exists, it returns it; otherwise it obtains the content from the origin and may cache it according to policy.