amazon ec2 - Multi-domain DNS configuration with Route53

I am configuring a few domain names in Route53 and am looking for some advice on best practices for setting things up. Here is the scenario:

Let's say domain1.com is my master corporate domain, and I also have domain2.com and domain3.com.

Suppose I have two Amazon EC2 instances defined as a web and database server, with elastic IPs of 11.11.11.11 and 22.22.22.22 respectively, and I want to address them externally as:

 prod-web01.domain1.com
 prod-db01.domain1.com

Let's further suppose that the website for domain1.com is hosted on one of the above instances, which means that I must set an A record for domain1.com (right?) to the elastic IP of the web instance. So I create record sets in Route53 like:

 domain1.com.                A         11.11.11.11
 prod-web01.domain1.com.     A         11.11.11.11
 prod-db02.domain1.com.      A         22.22.22.22

 www.domain1.com.            CNAME     prod-web01.domain1.com

Now, both domain2.com and domain3.com are also hosted on that web01 instance above, so I create record sets for them like:

 domain2.com.                A         11.11.11.11
 www.domain2.com.            CNAME     prod-web01.domain1.com.

and

 domain3.com.                A         11.11.11.11
 www.domain3.com.            CNAME     prod-web01.domain1.com.

This all works just fine, but it is not as elegant as I was hoping for. I am wondering if there is some way to set up this type of configuration in which there are fewer records pointing to direct IP addresses.

My understanding is that I can't use a CNAME record for the root of a domain (right?), so is there some other way to set things so that I only have one "hard" reference to each IP in my DNS infrastructure?

If not, does this seem like a smart setup? Or a dumb one? Feel free to tell me I'm dumb. :)

Answer

First things first, if you only have two instances (one web and one DB), you're doing it wrong. You should be setting up an elastic load balancer with a minimum of two application server instances behind it. Instances can (and do) fail from time-to-time. And you really should be using RDS for your persistent data store.

My understanding is that I can't use a CNAME record for the root of a
domain (right?)

You can, but it will frequently break stuff (esp email) in unexpected ways and shouldn't be done. This how I would do things:

 domain1.com.                A         11.11.11.11
 prod-web01.domain1.com.     A         11.11.11.11
 prod-db02.domain1.com.      A         22.22.22.22
 www.domain1.com.            CNAME     prod-web01.domain1.com

 domain2.com.                A         11.11.11.11
 www.domain2.com.            CNAME     domain2.com.

 domain3.com.                A         11.11.11.11
 www.domain3.com.            CNAME     domain3.com.