Design a global CDN strategy for a media-heavy product
Reported in Spotify European engineering loops. System design topic around edge caching, invalidation, and latency.
Interview scenario
Context for Spotify candidates:
Users across regions consume images and videos; reduce latency and origin cost.
Model answer
Try answering aloud first
Cover trade-offs, structure, and a concrete example before revealing the baseline response.
How to frame this at Spotify: Connect your answer to measurable impact, clarity of thought, and trade-offs the team cares about. Below is a strong baseline response you can adapt with your own project examples.
Serve static assets via CDN edge locations with cache keys that include path and relevant variants like quality or language. Use long TTL plus versioned asset names to avoid frequent hard invalidations.
For personalized content, combine CDN caching of public fragments with signed URLs and edge authorization checks. Keep origin shield and regional failover to protect backend during sudden spikes.
Track hit ratio, egress cost, and tail latency by geography. Mention purge strategy for urgent takedowns and stale-while-revalidate for smoother refreshes.
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