You already know how users find your website (DNS and Route 53). Now we'll see how to make your content reach them fast, wherever they are in the world. That’s the mission of CloudFront, AWS’s Content Delivery Network (CDN). We already mentioned it when talking about edge locations in Chapter 3; now we’ll understand it in depth.

Imagine your server is in Ireland (Chapter 3) and a user visits you from Japan. Every time they request something, the request has to cross half the world and come back. Even if it travels at the speed of light, that distance adds latency (delay): the website loads slowly for that user.

A CDN (Content Delivery Network) solves this by bringing the content closer to users. Instead of everyone reaching your distant server, the CDN stores copies of your content in many points distributed around the world (the edge locations from subchapter 3.3). Each user receives the content from the point closest to them.

CloudFront is AWS’s CDN, with hundreds of edge locations all over the planet.

Analogy: without a CDN it’s like having a single store in a city: all customers in the country have to travel there. With a CDN it’s like opening branches in every city: each customer goes to the nearest one. Much faster for everyone.

A distribution is the CloudFront configuration for your content: it defines where the content comes from (the origin), how it’s cached, which domain it uses, etc. It’s the “unit” you create in CloudFront.

The origin is the original source of your content, where CloudFront fetches it the first time. It can be:

• An S3 bucket (very common for static websites, remember subchapter 5.5).
• A load balancer (Chapter 13) in front of your servers.
• Any web server, even outside AWS.

The cache is what makes a CDN magical. The first time someone in a region requests a file, CloudFront fetches it from the origin and stores a copy in the nearby edge location. Subsequent requests from that area are served directly from the copy, without bothering the origin.

Double benefit:

• Speed: users receive the content from nearby.
• Less load on your origin: most requests are handled by the cache, not your server. Your origin works much less (and can be smaller and cheaper).

An important question: how long does CloudFront keep a copy before fetching it again from the origin? That’s controlled by the TTL (Time To Live), the cache’s “lifetime”.

• Long TTL: the copy lasts a long time. Maximum speed and minimum work for the origin, but changes take longer to show.
• Short TTL: the copy refreshes often. Changes are seen sooner, but the origin works more.

Practical rule: content that doesn’t change (images, CSS, videos, static website files) → long TTL. Content that changes often → short TTL or no cache.

What if you change a file and want it to update now, without waiting for the TTL? You can do an invalidation: you tell CloudFront “delete this copy from all edge locations,” and it will fetch it from the origin on the next request. Useful after publishing a new version of your website.

CloudFront shines especially with static content: images, videos, style sheets (CSS), JavaScript, downloadable files, and static websites (S3). This content is the same for all users, so caching it is ideal. It also speeds up dynamic content, though the gains are smaller there.

Real-world example: a digital newspaper with readers all over the world puts CloudFront in front of its website. Photos, videos, and design are served from each reader’s edge location (super fast), and the newspaper’s server only handles generating new articles. Result: the website flies for everyone and the server handles millions of visits without getting overloaded.

• CloudFront is AWS’s CDN: it brings your content closer to users by storing copies in edge locations around the world, reducing latency.
• A distribution is your CloudFront configuration; the origin is the original source (an S3 bucket, a load balancer, etc.).
• The cache is the key: the first request fetches the content from the origin and stores a copy; subsequent requests are served from the copy. Double benefit: speed + less load on the origin.
• The TTL defines how long a copy lasts (long for static content, short for changing content); invalidation forces an immediate refresh.
• It shines with static content (images, videos, CSS, JS, S3 websites), though it also speeds up dynamic content.

In the next subchapter, we’ll see how to make your site secure with HTTPS using free SSL/TLS certificates with ACM.