Oh right, we did have many app servers located with the DBs as well. They were stateless and numerous so could be anywhere. The datacentre with the bare metal did have dedicated links to the nearby AWS region we were using. At one point I think one of their redundant links got severed on purpose by accident, so things were slow for a while.

The microservices in AWS were feature-services that had their own datastores so only paid a single overall request latency than the many app-server to db queries per user request.