The key is to focus on the services that you can add value to over and above what the AWS managed services offer. There's no reason to futz around with building

The key is to focus on the services that you can add value to over and above what the AWS managed services offer. There's no reason to futz around with building and maintaining a load-balancer infrastructure if Amazon's ELB does everything you need (unlikely, I will admit). AWS and other cloud services just provide an additional set of tools that may or may not be useful.