I\'m building a solution that will be provided to several companies. Any company will have to point their domains (or just a sub-domain) to my server and then I\'ll handle p
Put Elactic Load Balancer in front of your application instance (even if you will use only one instance at the beginning).
Using your domain (the zone does not have to be hosted on Route53), create one CNAME (or ALIAS) record (for example myapp.example.com) and point it to your load balancer's domain name.
Simply tell your customers to CNAME their subdomain to your app dns name