[sehrope]

AWS supports VPC (virtual private network). It lets you setup sub groups of VMs that are only network accessible to each other with explicit endpoints open (ex: just HTTP open to an ELB). It's recommended for all new deployments. We use it in our cloud deployment of JackDB and it's really pleasant to use. Plus it makes it really easy to setup a bastion SSH proxy as an end point (vs. having all your instances publicly accessible).