AdvancedSystem-Design
45 min
Design a Content Delivery Network (CDN)
CDNCachingNetworkingSecurity
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Interview Question
Design a global CDN for static and dynamic content delivery, cache invalidation, SSL termination, and DDoS protection.
Key Points to Cover
- Edge PoPs, cache hierarchy, consistent hashing
- Cache invalidation and TTL strategies
- Dynamic content acceleration and edge compute
- TLS termination, cert rotation, key management
- DDoS detection, rate limiting, WAF integration
Evaluation Rubric
Strong caching hierarchy & invalidation25% weight
Dynamic acceleration & edge compute25% weight
TLS/DDoS/WAF security strategy25% weight
Global scale and failover handling25% weight
Hints
- 💡Think about cache key normalization to prevent evasion.
Common Pitfalls to Avoid
- ⚠️Over-reliance on TTL without considering explicit invalidation, leading to stale content.
- ⚠️Insufficient PoP coverage in key geographic regions, resulting in high latency for certain user bases.
- ⚠️Underestimating the complexity and performance impact of dynamic content acceleration techniques.
- ⚠️Inadequate security measures, leaving the CDN vulnerable to various types of DDoS attacks.
- ⚠️Lack of robust monitoring and alerting, hindering the ability to quickly detect and respond to performance degradations or security incidents.
Potential Follow-up Questions
- ❓How do you handle live video at the edge?
- ❓How to defend against large volumetric attacks?
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