Networking & Protocols
CDN and edge: free-recall review
Retrieval beats re-reading. For each prompt, say or write a full answer from memory before you open the model answer — the effort of recall is what makes the material stick.
Reconstruct the unit’s core mechanisms — Anycast vs GeoDNS, cache-key construction, origin shield, stale-while-revalidate, edge composition, and surgical purge — without looking back at the lessons.
- 01Anycast and GeoDNS both route a user to a nearby edge. Explain how each decides, and how they fail differently.
- 02What is EDNS Client Subnet, what does it fix, and what does it cost?
- 03How is a CDN cache key built, and why is a Vary: User-Agent header a footgun?
- 04What does an origin shield do, and how many origin requests does it generate when 200 edges in a region all miss the same cold URL at once?
- 05Explain the cache stampede and how stale-while-revalidate inverts it.
- 06Describe edge-side composition for a product page and why it beats one whole-page TTL, and how cache-tag purge fits a thousand-URL site.
If you could reconstruct each answer from memory, you hold the unit’s spine: Anycast and GeoDNS (plus ECS and smart routing) put the user on the right edge with different failure modes; the cache key (URL + method + Vary) decides reuse and high-cardinality Vary destroys it; the origin shield and stale-while-revalidate keep the herd off origin on expiry; edge-side composition serves fast pages with fresh fragments; and cache-tag purge makes invalidation tractable at scale.