Content Delivery Networks (CDNs) are globally distributed networks of edge servers that cache and deliver web content from locations nearest to end users, dramatically reducing latency and origin server load. CDNs sit between users and origin servers, serving as intelligent reverse proxies that make routing decisions based on real-time performance metrics, geographic proximity, and server health. The fundamental trade-off in CDN architecture is between cache hit ratio (how often content is served from cache) and content freshness — this tension shapes every caching policy, TTL setting, and invalidation strategy you'll configure.
What This Cheat Sheet Covers
This topic spans 15 focused tables and 114 indexed concepts. Below is a complete table-by-table outline of this topic, spanning foundational concepts through advanced details.
Table 1: Core CDN Architecture Components
The building blocks every CDN is assembled from, traced along the path a request actually takes. Edge servers at distributed PoPs are where users land; origin shield and tiered caches sit behind them to shelter the origin; and anycast, DNS routing, and the cache key decide which edge answers and what counts as the "same" cached object. Get the cache key wrong and your hit ratio collapses no matter how good the rest of the architecture is.
| Component | Example | Description |
|---|---|---|
cdn.example.com→ edge-sjc15.cdn.net | • Geographically distributed cache server at a Point of Presence • serves cached content to nearby users and fetches from origin on cache miss | |
origin.example.com:443 | • Source-of-truth server hosting original website content • CDN fetches content here on cache misses and periodically revalidates | |
Edge tier → Shield → Origin | • Additional caching layer between edge servers and origin that consolidates requests • dramatically reduces origin load by creating a three-tier hierarchy (Edge → Shield → Origin). | |
Regional cache in Singapore serves Asia-Pacific edges | • Hierarchical caching architecture with regional mid-tier caches • edge servers check regional cache before hitting origin, improving cache hit ratio for multi-region deployments |