Root domain, also know as top level domain, naked domain or DNS zone apex, is your domain name without any subdomains. In our case our product web site and blog can be found at the www subdomain http://www.meetin.gs/ but our web application is being hosted at the root domain, namely just “meetin.gs”.
Amazons Elastic Load Balancer (ELB) has seemed like a very tempting offer for a long time since providing IP level fail-over on the web application front-end is a lot of work to achieve reliantly. Unfortunately it was previously impossible to use ELB to serve root domains because it would have required one to point the root domain to the ELB by a CNAME DNS entry and there is practically no sane way of using CNAMEs for root domains. For us that meant the service was of no use.
As of May 24 2011 Amazon seems to have found a way to fix this problem by adding a special ‘Alias’ entry to their own Route 53 DNS service. This allows you to set your root domain to return the A record associated with the ELB.
Currently it seems like using Amazons Route 53 DNS to serve your domain’s DNS requests is the only off the shelf way for serving root domains with ELB. I believe it would be technically possible for other DNS service providers to achieve almost the same level of service by implementing a similar ‘Alias’ functionality for mirroring the A records returned for an another domain with a small TTL but I’m not sure if it makes business sense. The only other product I know which would benefit from this is Google App Engine as it suffers from the same problem of not being able to serve root domains due to reliance on CNAMEs to point domains. Other cloud load balancing providers (at least Rackspace and GoGrid) seem to be doing load balancing tied to an actual IP address instead of a domain CNAME.
Also as a note for people trying this out: At this date Amazon Route 53 does not seem to have a graphical user interface on the AWS management console. It took me a while to figure out that you really have no other way of controlling it than using the Perl script they provide to send XML to their web service. Ouch. Hopefully a graphical interface will be added in the near future!