Content Delivery Network (CDN)

Table of Contents

CDN

A Content Delivery Network (CDN) is a geographically distributed group of servers that caches website content to deliver it to users from a server closer to them, improving website speed and performance. By storing copies of files like images, videos, and scripts on “edge servers” in “Points of Presence” (PoPs) around the world, CDNs reduce latency, decrease load times, and lower bandwidth consumption for origin servers.

How it works

  1. Caching: A CDN stores copies of a website’s static content (like images and CSS files) on its servers. When a user requests this content, it is served from the nearest CDN server, or “Point of Presence” (PoP), instead of the original hosting server.
  2. Geographic distribution: The CDN network has servers in many different locations to be closer to users globally, which drastically cuts down the physical distance data must travel, resulting in faster load times.
  3. Dynamic acceleration: Advanced CDNs also use optimized routing and other techniques to speed up the delivery of dynamic content, which changes based on user preferences or location.

Key benefits

  1. Improved website performance: By reducing latency, CDNs make websites load faster and feel more responsive.
  2. Increased reliability and availability: Distributing content across multiple servers helps a website remain available even during traffic spikes or origin server issues.
  3. Reduced bandwidth costs: Offloading traffic from the origin server to the CDN reduces the amount of data the main server has to serve, which can lower hosting costs.
  4. Enhanced security: CDNs can help protect against attacks like Distributed Denial of Service (DDoS) by absorbing and mitigating malicious traffic before it reaches the origin server.

Reading material

  1. https://www.cloudflare.com/learning/cdn/what-is-a-cdn/
  2. https://aws.amazon.com/getting-started/hands-on/lightsail-cdn/
  3. https://en.wikipedia.org/wiki/Content_delivery_network

Cloudflare resolves outage that impacted thousands, ChatGPT, X and more

By MICHELLE CHAPMAN

Updated 2:14 PM EST, November 18, 2025

https://apnews.com/article/cloudflare-outage-x-openai-9335e8e0da2a0027d1fbac5eb97d11ae

A widely used Internet infrastructure company said that it has resolved an issue that led to outages impacting users of everything from ChatGPT and the online game, “League of Legends,” to the New Jersey Transit system early Tuesday.

At 12:44 p.m. EST, Cloudflare said its engineers no longer saw some of the issues plaguing its customers, but that they were continuing to monitor for any further problems.

Others platforms that experienced outages Tuesday included the social media site X, Shopify, Dropbox, Coinbase, and the Moody’s credit ratings service. Moody’s website displayed an Error Code 500 and instructed individuals to visit Cloudflare’s website for more information.

New Jersey Transit said parts of its digital services including njtransit.com, may be temporarily unavailable or slow to load. And New York City Emergency Management said there are reports city services being impacted by the outage. The city is continuing to monitor for disruptions.

In France, national railway company SNCF’s website has been affected. The company warned customers that “some information and schedules may not be available or up to date. Our teams are working to restore these services as quickly as possible.”

Cloudflare, based in San Francisco, works behind the scenes to make the internet faster and safer, but when problems flare up “it results in massive digital gridlock” for internet users, cybersecurity expert Mike Chapple said.

While most people think there’s a direct line between their digital device and a website, what actually happens is that companies like Cloudflare sits in the middle of those connections, he said.

Cloudflare is a “content delivery network” that takes content from 20% of the world’s websites and mirrors them on thousands of servers worldwide, said Chapple, an information technology professor at the University of Notre Dame’s Mendoza College of Business.

“When you access a website protected by Cloudflare, your computer doesn’t connect directly to that site,” Chapple said. “Instead, it connects to the nearest Cloudflare server, which might be very close to your home. That protects the website from a flood of traffic, and it provides you with a faster response. It’s a win-win for everyone, until it fails, and 20% of the internet goes down at the same time.”

Last month Microsoft had to deploy a fix to address an outage of their Azure cloud portal that left users unable to access Office 365, Minecraft and other services. The tech company wrote on its Azure status page that a configuration change to its Azure infrastructure caused the outage.

And Amazon experienced a massive outage of its cloud computing service in October. The company resolved the issue, but the outage took down a broad range of online services, including social media, gaming, food delivery, streaming and financial platforms.

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