Interesting comment about Microsoft Azure latency.
I have found AWS to be very fast in every dimension. nderground uses Elastic Beanstalk (Linux and Tomcat) with two t2.micro instances, RDS/Postgres, DynamoDB, S3 and the Simple Email System (SES) (among other things). The network connectivity between the components in the AWS cloud is very fast. Perhaps because I have off-loaded computation into other components, I have yet to see any real load on the t2.micro instances, which has been a surprise. I though that I would have to move up to t2.medium instances.