Route 53 - CNAME vs Alias¶

AWS Resources (Load Balancer, CloudFront...) expose an AWS hostname:
- lb1-1234.us-east-2.elb.amazonaws.com and you want myapp.mydomain.com
CNAME:
- Points to a hostname to any other hostname (app.mydomain.com => test.anything.com)
- Only for non root domains (aka something.mydomain.com)
Alias:
- Points a hostname to an AWS Resource (app.mydomain.com => test.mydomain.com)
- Works for root domain and non root domains (aka mydomain.com)
- Free of charge
- Native health checks

Route 53 - Alias Records¶

Maps a hostname to an AWS Resource
An extension to DNS functionality
Automatically recognizes changes in the resource's IP address
Unlike CNAME, it can be used for the top node of a DNS namespace (Zone Apex), e.g. example.com
Alias Record is alwayts of type A/AAAA for AWS resources (IPv4 / IPv6)
Cannot set TTL, it's set automatically by route 53