System design interview question
Design a Distributed Content Delivery and Cache Invalidation System like Cloudflare's Edge Network
Design a global content delivery system that serves cached assets and web content to 500M monthly users across 6 continents, handling 2M requests/second with sub-100ms latency requirements. The system must support real-time cache invalidation when origin content updates, handle cache coherency across 200+ edge nodes, manage cost-efficient storage with tiered caching (hot/warm/cold), and provide observability for cache hit rates, staleness detection, and origin failover. Consider how to handle unpredictable viral traffic spikes, partial cache failures in specific regions, and the tension between eventual consistency and low latency during invalidation events.
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