Explain Content Delivery Networks (CDN) in Interviews

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CDNs in Technical Interviews

Common Interview Questions

CDNs are a frequent topic in system design and web development interviews, especially at FAANG companies. Here are common questions and concise answers:

1. What is a CDN and why is it used?
   • A CDN is a network of distributed servers that caches content closer to users to reduce latency, improve performance, and enhance scalability.
2. How does a CDN improve website performance?
   • By serving content from edge servers near the user, CDNs minimize data travel distance, reducing load times.
3. What are the key components of a CDN architecture?
   • Edge servers, origin servers, DNS, load balancers, and caching mechanisms.
4. How does caching work in a CDN?
   • Content is cached on edge servers after the first request. Subsequent requests are served from the cache, reducing origin server load.
5. What is the difference between a CDN and a regular web server?
   • A web server hosts content in one location, while a CDN distributes cached content globally for faster delivery.
6. How does a CDN handle high traffic and DDoS attacks?
   • CDNs distribute traffic across multiple servers and use scrubber servers to filter malicious traffic, mitigating DDoS attacks.

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Advanced CDN Topics

For senior roles or advanced interviews, you may encounter questions on:

• CDN Routing Techniques:
  • Anycast Routing: Directs traffic to the nearest server using a single IP address.
  • DNS-based Routing: Uses DNS to select the optimal edge server based on location or load.
  • GeoIP-based Routing: Maps user IP addresses to nearby servers.
• Caching Mechanisms:
  • Time-to-Live (TTL): Determines how long content stays cached before refreshing.
  • Cache Invalidation: Removes outdated content to ensure freshness.
  • Cache Control Headers: Allow fine-tuned control over caching behavior.
• CDN Network Topologies:
  • Flat Topology: All edge servers connect directly to the origin.
  • Hierarchical Topology: Uses intermediate servers for caching and distribution.
  • Mesh Topology: Servers communicate peer-to-peer for redundancy.
  • Hybrid Topology: Combines elements of the above for flexibility.
• Dynamic Content Acceleration: Modern CDNs use edge computing and caching rules to accelerate dynamic content, such as personalized web pages or API responses.

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Conclusion

Mastering CDNs is essential for excelling in technical interviews, particularly for roles in web development, system design, or cloud engineering. By understanding their architecture, benefits, and advanced concepts, you can confidently explain how CDNs optimize content delivery and handle real-world challenges like traffic spikes and security threats. Practice articulating these concepts clearly, as interviewers value both technical depth and communication skills.

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