CDNs Demystified: How They Make the Internet Faster

A Content Delivery Network (CDN) is a network of geographically distributed servers that collaborate to provide rapid delivery of internet content.

A CDN consists of a distributed array of servers located in multiple data centers across the world. Its primary objective is to deliver web content, such as images, videos, scripts, and other static files, to users based on their geographical location. This reduces latency and accelerates load times.

You can think of a CDN as similar to a computer’s memory module or a web cache server; all are designed to save time. For instance, Amazon is a global website with users in America and China. However, due to the distance between the client and the server, Chinese users might experience slow browsing speeds when accessing the Amazon website. To understand how CDNs work, let’s clarify these terms:

 

Origin Server: The origin server is the main, central server (or group of servers) where your website, application, or online service stores all its original content. It serves as the primary source of truth for your digital assets.

Edge Server: Edge servers are part of the CDN’s distributed network and are situated in various geographic locations worldwide, close to end users. They serve as local copies or “caches” of your content.

 

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How a CDN Syncs and Distributes Data Between Origin and Edge Servers:

 

Time-to-Live (TTL): Each piece of cached content has a TTL, which specifies the duration it can be stored on the edge server before it expires. Once the content expires, the edge server retrieves the updated version from the origin server.

Purge or Invalidation: You can manually purge cached content from edge servers or invalidate it, which forces the CDN to fetch the latest version from the origin server.

Push vs. Pull: CDNs can employ either a “push” method, where updated content is proactively sent to edge servers, or a “pull” method, where edge servers request updates from the origin server only when necessary.