Content Delivery Network (CDN)
A CDN caches and serves content from edge locations near users, reducing latency and origin load while improving reliability and security.
A content delivery network (CDN) is a distributed network of servers, called points of presence or edge nodes, placed in many locations around the world. The CDN caches copies of content close to users so requests are served from a nearby node instead of the distant origin server, reducing latency and lightening the load on the origin.
How It Works
When a user requests an asset, DNS or anycast routing directs the request to the nearest edge node. If the node has a fresh cached copy, it returns it immediately. If not, the node fetches the asset from the origin, serves it, and caches it for future requests, governed by time-to-live and cache-control headers. CDNs cache static assets such as images, scripts, and video, and increasingly accelerate dynamic content and run code at the edge. Cache invalidation, or purging, refreshes content when the origin changes.
Why It Matters
CDNs are essential for fast, reliable global delivery. They cut page load times, absorb traffic spikes, and reduce origin bandwidth and cost. They also improve resilience and security: by fronting the origin, a CDN can absorb distributed denial-of-service attacks, terminate TLS, and apply a web application firewall. The main considerations are correct cache configuration, handling personalized or frequently changing content, and ensuring cached data does not leak sensitive information.
Related Terms
A CDN is closely related to edge computing, relies on caching, and works alongside load balancers and regions for global performance.