Amazon Route 53 alias records provide a Route 53–specific extension to DNS functionality. Alias records let you route traffic to selected AWS resources, such as CloudFront distributions and Amazon S3 buckets. They also let you route traffic from one record in a hosted zone to another record.
Note that alias record change are instant as they internal to AWS.
When you use an alias record to route traffic to an AWS resource, Route 53 automatically recognizes changes in the resource. For example, suppose an alias record for example.com points to an ELB load balancer at lb1-1234.us-east-2.elb.amazonaws.com. If the IP address of the load balancer changes, Route 53 automatically starts to respond to DNS queries using the new IP address.
When Route 53 receives a DNS query for an alias record, Route 53 responds with one or more values for that resource:
Unlike a CNAME record, you can create an alias record at the top node of a DNS namespace, also known as the zone apex. For example, if you register the DNS name example.com, the zone apex is example.com. You create an alias record for example.com that routes traffic to www.example.com.