I am writing a Facebook application that would use a Postgres DB along with Facebook APIs and run on Amazon EC2. (and I am hoping for heavy loads )

With Java, I know that DB would be my primary bottleneck and concurrency limitations of Tomcat would be the secondary bottleneck. I could alleviate DB issues with caching and concurrency issues with horizontal scaling . ( but this would add to my EC2 costs).

How would Erlang or Haskell help in this situation ? ( assuming I am able to master the learning curve).