Interview Questions/System Design/Content Delivery Network (CDN)

Content Delivery Network (CDN)

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Medium

Content Delivery Network (CDN)

Design a Content Delivery Network (CDN) that serves static and dynamic content with low latency globally. Functional Requirements: - Cache and serve static content (images, CSS, JS, videos) from edge servers - Origin pull: fetch from origin server on cache miss - Cache invalidation / purging - Support for custom domains and SSL certificates - Analytics: hit rate, bandwidth, latency per edge location Non-Functional Requirements: - Sub-100ms response time for cached content globally - 99.99% availability - Support for terabytes of cached content per edge node - Handle traffic spikes (e.g., viral content) Scale: - 200+ edge locations worldwide - 10M requests per second globally - Petabytes of content served daily

Examples

Example 1

How would you handle video streaming (large files, seek support, adaptive bitrate)?

Approach hint

Think about how a user's HTTP request gets routed to a server that's geographically close to them. DNS plays a key role here.

Common mistake

Skipping assumptions, edge cases, or trade-offs can make an otherwise good answer feel incomplete.

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