System designMediumsd-g047

Subject CdnLevel Mid–Senior~35 minCommon in Storage & CDN interviewsIndustries Technology, Software development

Question

Design CDN caching for a news site that gets sudden traffic spikes (10x in minutes when a story breaks) serving mostly static article HTML plus a few personalized fragments. Article HTML can be cached for minutes but must be purgeable within seconds when an editor fixes a factual error. Personalization (logged-in name, region) must not leak between users. Explain your cache-key design, how you protect the origin during a spike, and how you purge fast.

What a strong answer looks like

Clarify scale and constraints first. Propose a clean component breakdown, then go deep on the hard parts — data model, bottlenecks, consistency, failure modes — and name the trade-offs you are making.

Learn the concepts

Narrate your design

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Run or narrate your approach, then ask the coach.