[Fargate] [request]: Document the specifications of the hosts used to execute Fargate tasks

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**Tell us about your request**

Documentation for the specifications of the hosts used to execute Fargate tasks

**Which service(s) is this request for?**
Fargate

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**

When migrating applications from EC2 instances to Fargate initial estimates on task requirements (number of tasks, CPU value) is made more difficult without specifications on the underlying hosts used. This initial estimation often needs to come before more detailed performance testing is approved.

It's also not clear how much network, CPU and memory performance can vary across different Fargate tasks depending on the underlying host they are scheduled to run on.

Currently the only information available has been derived from third party testing:

https://www.stormforge.io/blog/aws-fargate-network-performance/

https://www.scalefactory.com/blog/2021/05/12/what-powers-ecs-fargate/

For EC2 the [EC2 instance types](https://aws.amazon.com/ec2/instance-types/ ) page provides information related to networking, storage bandwidth and machine specifications. It would be good to have insight into what underlying instance types are used for Fargate or if there isn't a direct correlation then a similar 'Fargate Instance Type' page.

**Are you currently working around this issue?**

Reading 3rd party blog posts and our own testing, but some authoritative documentation would be preferred.

No files, tests, or entry points are named. Start by reviewing the existing Fargate documentation and the linked AWS EC2 instance specifications, then determine what authoritative host, network, CPU, and memory details can be documented; done means the relevant Fargate documentation clearly covers the requested specifications and variability.

Written by the indexing model from the issue text.