CDN

How this question breaks down

1. 1Edge cachingCore17 minKeep copies of responses on servers close to users, so most requests are answered in one short round trip and never reach the origin.
2. 2Push vs pullCore14 minDecide whether content reaches the edge on demand, when the first user asks for it, or ahead of time, because you already know it will be wanted.
3. 3InvalidationCore20 minBound how stale an edge copy can be, and change content before its TTL runs out, by versioning URLs, purging by URL or tag, and serving stale while the edge revalidates.
4. 4Origin shieldCore19 minPut one more cache tier between hundreds of edge PoPs and the origin, so a miss everywhere becomes one fetch, and a burst of identical requests collapses into one.

Work through the parts in order and you’ve covered the full design. Each part is one topic.