Definition: Geographically distributed network of servers that delivers cached content from the closest location to the user, reducing latency and absorbing traffic spikes.
— Source: NERVICO, Product Development Consultancy
What is a CDN
A CDN (Content Delivery Network) is a geographically distributed network of servers that stores cached copies of a website’s or application’s content. When a user requests a resource, the CDN serves it from the server closest to their physical location, instead of routing the request to the origin server. This drastically reduces latency and improves load times.
Providers like Cloudflare, AWS CloudFront, Fastly, and Akamai operate networks with hundreds of points of presence (PoP) distributed worldwide.
How it works
The CDN operates as an intermediate layer between the user and the origin server. The first time a user requests a resource (image, CSS file, HTML page), the CDN fetches it from the origin server and stores it in cache at the nearest point of presence. Subsequent requests for the same resource from the same region are served directly from the CDN cache, without contacting the origin server.
Cache policies determine how long each resource is kept. Static files (images, fonts, JavaScript) can be cached for months. Dynamic content may have a TTL of seconds or minutes. Modern CDNs also offer edge computing capabilities, allowing server-side logic to run at points of presence.
Why it matters
Network latency has a direct impact on user experience and business metrics. Every additional 100ms of load time reduces conversions by 1% to 7% according to various studies. A CDN can reduce latency from 200ms to under 20ms for users far from the origin server. It also absorbs traffic spikes that could overwhelm the origin server.
Practical example
A Spanish company launches a marketing campaign in Latin America. Without a CDN, users in Mexico City experience 250ms latency loading images from a server in Madrid. With a CDN configured, images are served from a point of presence in Mexico City with 15ms latency. The site loads 4 times faster for those users, and the origin server receives 85% less traffic because the CDN absorbs static content requests.