Using AWS ALB to have subdomains pointing to different target groups

Question

Right now I have a domain (example.com) that I have hosted on Google Domains, but uses Amazon's Route 53 DNS servers, and I've created a hosted zone & registered an SSL certificate for free with ACM. So I got it to take requests for example.com and forwards them to a target group (EC2 instance).

I'd like to expand this into:

• staging.example.com
• prod.example.com

where each has its own target group it points to.

Is this possible with an ALB? How would I encode this into the load balancer's routing rules?

(Also: would I have to re-verify the SSL cert for the subdomains?)

Answer 1

You route each subdomain to different target group using Listener Rules

When you add a Listener Rule, set a condition for Host header and select the subdomain you want to use e.g. staging.example.com and select Forward to as your target group.

Regarding SSL, you won't need to create a new certificate as long as you have the certificate for *.example.com attached to the listener (see View/Edit certificates)

Answer 2

Yes, it is possible. Just create another recordset in your hosted zone (presumably the same way you did it for example.com) for staging and for prod. As for the certificate issue, you will need a wildcard certificate if you want to use the same certificate for all 3 hosts (example.com, staging.example.com and prod.example.com).