Answer Key: CDN System

Back to Exercises

Exercise 1: Design Improvements

Question: How would you improve this design? What tradeoffs?

Answer

Potential improvements:

  1. Add More Edge Locations: Increase edge coverage
  2. Implement Cache Warming: Pre-warm cache for popular content
  3. Add Analytics: Enhanced analytics and monitoring
  4. Optimize Compression: Better compression algorithms

Tradeoffs: - Higher cost vs better performance - More complexity vs simpler architecture - More maintenance vs better features

Answer: Add more edge locations, implement cache warming, enhance analytics, optimize compression. Balance cost vs performance.

Exercise 2: Handle Cache Invalidation

Question: How do you handle cache invalidation for frequently updated content?

Answer

Cache invalidation strategies:

  1. Versioned URLs: Use versioned URLs (e.g., /v1/image.jpg)
  2. Selective Invalidation: Invalidate only changed content
  3. TTL Optimization: Use appropriate TTL for content type
  4. Cache Tags: Use cache tags for grouped invalidation

Answer: Use versioned URLs, invalidate selectively, optimize TTL, use cache tags for grouped invalidation.

Exercise 3: Optimize Costs

Question: How would you reduce costs by 30%? What tradeoffs?

Answer

Cost optimization strategies:

  1. Optimize Cache Hit Rate: Increase cache hit rate to reduce origin load
  2. Use Regional Storage: Use regional instead of multi-region storage
  3. Optimize Compression: Better compression to reduce bandwidth
  4. Reduce Origin Load: Cache more content, reduce origin requests

Tradeoffs: - Lower cache hit rate vs cost savings - Less redundancy vs cost reduction - More optimization effort vs cost savings

Answer: Optimize cache hit rate, use regional storage, optimize compression, reduce origin load. Balance cost vs performance.