CDN
A network of servers distributed globally that caches content close to users. Netflix uses CDNs to stream video from servers near you, not from one central location.
What is CDN?
A network of servers distributed globally that caches content close to users. Netflix uses CDNs to stream video from servers near you, not from one central location.
CDN is a foundational concept that sits in the Caching Strategies area of system design. Engineers reach for it whenever they need to reason about real-world trade-offs in that space — not just for textbook correctness, but because real production systems at companies like Netflix, Amazon, and Google make these decisions every day.
If you want to go deeper than this definition — with diagrams, code, and a quiz to lock it in — work through the "CDN" lesson linked below. It walks through the why, the mechanism, the trade-offs, and how the giants actually use it in production.
Learn CDN in depth
Full interactive lesson with diagrams, code examples, real-world references, and a quiz.
Open the CDN lessonRelated lessons
Lessons that touch on CDN as part of a larger topic.
Design a Content Delivery Network
Design a CDN from scratch - edge caching, origin shield, cache purging, anycast routing, TLS termination, and global distribution
capstone · capstone
Content Delivery Network (CDN)
Serve content from edge locations worldwide for sub-50ms response times using Cloudflare, CloudFront, and edge caching
foundation · load balancing proxies
Design YouTube/Netflix
Design a video streaming platform - transcoding pipelines, adaptive bitrate streaming, CDN architecture, and recommendation engines at planetary scale
capstone · capstone
Server-Side Caching
Caching at the server and infrastructure level, reverse proxies, CDNs, and full-page caching
foundation · caching strategies
Edge-Side Includes (ESI)
Assembling pages from fragments at the CDN edge, mixing cached and dynamic content at the network layer
intermediate · web content delivery
See also
Related glossary terms you might want to look up next.
Caching
Storing frequently accessed data in a faster storage layer so you don't have to fetch it from the original (slower) source every time.
Latency
The time delay between sending a request and getting a response. Amazon found every 100ms of extra latency costs 1% in sales.
DNS
The phonebook of the internet. Translates human-readable domain names (google.com) into IP addresses that computers understand.