About two years ago I was working on a service that was suppose to expose some private APIs. These APIs did not require any authentication process, but were meant to be consumed exclusively by other services that we own.
What this meant was that our services could make API calls to my-private-service.internal and this would resolve to some sort of private IP address (e.g. 10.10.3.27).
Implications of moving a private AWS ECS container to AWS Lambda Fast-forward 2 years and AWS has improved the AWS Lambda cold start drastically, which means that we no longer need containers running 24/7 to provide such a private API.