We begin the chapter on content delivery and DNS: how users reach your application quickly, reliably, and securely. The first piece is DNS, the "phone book of the internet," which in AWS is managed by the Route 53 service. Without DNS, the internet would be a chaos of numbers impossible to remember.

When you type www.google.com in your browser, your computer doesn't know where that site is: it needs an IP address (a number like 142.250.184.4). The DNS (Domain Name System) is the system that translates domain names into IP addresses.

Analogy: DNS is like your phone's contact list. You call "Mom," you don't memorize her phone number. The contact list translates the name into the real number. DNS does the same with websites: you remember mywebsite.com, and DNS translates it to the server's IP.

Route 53 is AWS's DNS service (the "53" comes from the port DNS uses). With it you can:

• Register domains (buy myshop.com).
• Manage the DNS records of your domains.
• Intelligently route traffic to your resources (with the routing policies we'll see).

It's the gateway for users to your application.

A domain has several records, each with a function. These are the ones you need to know:

The two most common in day-to-day use are A (name → IP) and CNAME (name → another name).

Route 53 adds a very useful proprietary type: the Alias record. It's similar to a CNAME, but designed to point directly to AWS resources (a load balancer from Chapter 13, a CloudFront distribution, an S3 bucket...). It has advantages: it works at the root of the domain (where a CNAME can't) and has no additional query cost.

To start: use A/Alias records to point your domain to your AWS resources (a load balancer, CloudFront). This is the most common.

Here's what makes Route 53 special. It doesn't just translate names: it can decide which IP to respond with according to different criteria, using routing policies.

The basic one: one name → one address. No additional logic. For most simple websites, this is enough.

Distributes traffic among several destinations according to percentages you define. Ideal for gradual deployments.

Example: you want to test a new version of your website with a few users before launching it to everyone (a "canary"). You send 10% of the traffic to the new version; if all goes well, you increase the percentage. This is called a canary deployment.

Sends each user to the server that gives them the lowest latency (the fastest for them), usually the geographically closest. Recall the concept of latency from Chapter 3.

Sends users to a destination according to their country or region. Useful for showing localized content or complying with regulations.

Has a primary and a backup destination. If the primary fails (detected with a health check, we'll see this in subchapter 16.4 and in Chapter 26), Route 53 automatically redirects to the backup.

This is key for high availability (Chapter 26).

• DNS translates domain names into IP addresses (the "contact list" of the internet); Route 53 is AWS's DNS service and the gateway to your application.
• Key records: A (name → IPv4), CNAME (name → another name), and AWS's Alias (points to AWS resources like load balancers or CloudFront, with no extra cost).
• Routing policies direct traffic intelligently: Simple, Weighted (percentages, canary deployments), Latency (fastest server), Geolocation (by country), and Failover (primary + backup for high availability).
• To start: A/Alias records pointing to your AWS resources, with Simple policy.

In the next subchapter, we'll see how to accelerate the delivery of your content to users around the world with the CloudFront distribution network.