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Content Delivery Networks (CDNs)

Scope

A globally distributed network of proxy servers that cache and serve content from locations closer to the user.

Why This Topic Exists

CDNs are fundamental to modern web performance, significantly decreasing latency and improving the user experience by reducing the physical distance between the user and the server. They also play a crucial role in the scalability and reliability of web applications.

Core Tradeoffs

Push vs. Pull caching strategies
Cost vs. performance and feature set (e.g., DDoS protection, edge computing)
Granularity of cache invalidation vs. simplicity

Common Failure Modes

Misconfigured caching rules leading to stale content
Increased latency if user is routed to a non-optimal edge location
CDN outage causing widespread unavailability
Ineffective cache invalidation leading to inconsistent data

Interview Signals

Strong candidates will discuss the nuances of push vs. pull CDNs, cache invalidation strategies (e.g., TTL, explicit invalidation), how CDNs handle cache misses, and the security benefits and risks associated with using a CDN.

Caching
Performance
Scalability
Security