A CDN keeps copies of your responses in data centres close to your users, so a request from Chennai is answered in Chennai instead of crossing an ocean to your origin. That's the whole idea, and every cloud sells a version of it. The differences that matter are smaller and more practical: what each one puts in the cache key, how it charges you, what code you can run at the edge, and what happens on a cache miss when ten thousand people ask for the same thing at once.
The course covers the concept in CDNs and where caches live. This page compares the products.
Side by side
| AWS CloudFront | Google Cloud CDN | Azure Front Door | Self-hosted or third-party | |
|---|---|---|---|---|
| What it is | A standalone CDN with its own distributions | A feature you switch on for a global external Application Load Balancer | A global layer 7 entry point that does CDN, routing and WAF in one (overview) | Varnish or nginx in your own PoPs; or Cloudflare, Fastly, Akamai |
| Origins | S3, load balancers, any HTTP server | Backend services and Cloud Storage buckets behind the load balancer | Any HTTP origin, including private ones over Private Link | Anything you can reach |
| Code at the edge | CloudFront Functions and Lambda@Edge | Service Extensions on the load balancer | Rules engine with regular expressions and server variables | Cloudflare Workers, Fastly Compute, VCL |
| What you pay per | Requests and GB out, by viewer region (pricing); or a flat monthly plan | GiB of cache data transfer out, GiB of cache fill, and cache lookups (pricing) | A tier fee plus usage; egress from Azure regions to Front Door is included (overview) | Your hardware and transit, or the vendor's contract |
| Retired products to avoid | None | None | Azure Front Door (classic) retires 31 March 2027; Azure CDN Standard from Microsoft (classic) retires 30 September 2027 |