what-is-a-cdn

CDN caching is the process of storing copies of website or application content on CDN edge servers so users can access that content faster.

Caching is one of the most important functions of a content delivery network. It allows frequently requested content to be served from edge locations instead of being fetched from the origin server every time.

Cache Hit

A cache hit happens when the requested content already exists on the CDN edge server. For example, if a user requests a product image and that image is already cached at a nearby edge server, the CDN can deliver it immediately. This improves speed and reduces the load on the origin server.

Cache Miss

A cache miss happens when the requested content is not available in the edge cache. In this case, the CDN retrieves the content from the origin server, delivers it to the user, and may store a copy at the edge for future requests.

TTL

TTL, or Time to Live, defines how long cached content should stay on the CDN edge server before it expires. Static files such as logos, JavaScript files, CSS files, and product images may use a longer TTL because they do not change frequently. Dynamic content or frequently updated files may need a shorter TTL.

Cache Purge

A cache purge removes cached content from CDN edge servers. This is useful when content changes and users need to see the latest version immediately, such as after updating a product image, replacing a software file, or correcting a web page.

A CDN cache can include images, CSS files, JavaScript files, HTML pages, videos, software downloads, documents, game patches, and selected API responses depending on cache rules.

A CDN service is a managed content delivery solution provided by a CDN provider. It gives businesses access to a distributed network of edge servers, caching features, traffic routing, performance optimization, analytics, and security capabilities.

Instead of building and maintaining a global delivery infrastructure by themselves, companies can use a CDN service to deliver content through an existing network of edge servers.

A CDN service usually includes static content delivery, dynamic content acceleration, video delivery, software and large file distribution, DNS-based traffic routing, origin protection, DDoS protection, web application firewall integration, TLS and HTTPS support, logs, and performance analytics.

For a small website, a CDN service can improve page loading speed. For a large business, it can become a critical part of global digital infrastructure.

A good CDN service should help users access content quickly, even during peak traffic, regional network congestion, or unexpected origin server pressure.