If you have your domain registered at a registrar other than Amazon and would like to use the subdomain of that domain to point to your cluster, you will need to modify your name servers entries in your registrar. This would require a new hosted zone subdomain to be created in Route 53 and then migration of this subdomain's name server records to your registrar.
Similar to the subdomain on the AWS-hosted domain, let's create a subdomain first, by executing the following command:
$ aws route53 create-hosted-zone \ --name myservice.mydomain.com \ --caller-reference $ID | jq .DelegationSet.NameServers
The output of the previous command will list the name servers for the subdomain. ...