Started with edge nodes and cache invalidation, which felt right, but I got pretty tangled up explaining how origin pull vs push models interact with TTL policies.
Start by clarifying requirements and scale, then outline the high-level architecture covering DNS routing, edge caching, and origin fetch. Dive into key components like cache hierarchy, consistency, and performance optimizations, and discuss trade-offs for each design decision.
Pro tip: Emphasize how you would measure and monitor CDN performance (e.g., cache hit ratio, latency percentiles) and iterate based on data, showing a production mindset.
Ask about scale (QPS, data volume), content types (static/dynamic), geographic distribution, and consistency needs to scope the design.
Sketch the main components: DNS-based global load balancing, edge servers, mid-tier cache, and origin servers, and explain the request flow.
Detail edge caching strategies (TTL, eviction), cache hierarchy, and how to handle dynamic content and cache invalidation.
Discuss horizontal scaling, fault tolerance, and how to handle traffic spikes and failures (e.g., anycast, health checks).
Compare design choices (e.g., push vs. pull, consistency vs. latency) and suggest optimizations like compression, HTTP/2, and edge compute.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.