Prerequisites
What it is
A content delivery network is a global layer of edge servers that cache and serve assets near users. CDNs commonly deliver images, video segments, JavaScript, downloads, and sometimes whole pages.
Why it matters
Distance adds latency. A CDN moves hot content closer to users and reduces repeated traffic to the origin, improving speed, reliability, and cost.
How it works
Requests go to an edge location. If the object is cached and fresh, the edge returns it. If not, it fetches from origin, stores the response according to cache headers, and serves future requests locally.
When to use it
Use a CDN for static assets, media delivery, high-traffic public content, and APIs where edge caching is safe.
Tradeoffs / failure modes
Stale content, purge delays, cache key mistakes, and origin shielding gaps are the classic problems. Dynamic or personalized responses need careful caching rules.
Tiny example
Netflix can serve video chunks from nearby Open Connect appliances instead of pulling every stream from a central cloud region.
Related guides and systems
See CDN & Asset Delivery, Video Transcoding, Custom Domains, Netflix, YouTube, Instagram, Google Photos, and Zoom.
Seen in deeper dives
Capability
CDN & Asset Delivery
Origin shielding, cache hierarchies, purging strategies, and global content distribution
Capability
Custom Domains
Let users map their own domains to your SaaS with DNS verification and automatic TLS
Capability
Video Transcoding Pipeline
Adaptive bitrate encoding, queue-based processing, and HLS/DASH delivery for streaming
Case Study
Google Photos
AI-powered photo storage, search, and memories for billions of images
Case Study
Photo and video sharing at massive scale with real-time feeds
Case Study
Netflix
Global video streaming with personalized content delivery
Case Study
YouTube
The world's largest video platform serving billions of hours daily
Case Study
Zoom
Proprietary multimedia routing for reliable video conferencing at any scale
Related concepts
Load Balancer
Distribute traffic across healthy servers without making clients know where work runs.
Write-Through Cache
Keep cache and database updated together so reads can trust the cached value.