I thought the chosen example for idempotent requests was a bit funny as I don't think POST is necessarily idempotent and depending on your specific use case making it so may or may not be easy.
The article doesn't mention POST. It says "the first time we call it the VM is created. The second time it is called the system detects that the VM already exists and simply returns without error". Makes more sense to assume it means PUT, defined as "The HTTP PUT request method creates a new resource or replaces a representation of the target resource with the request payload"
...and the given example of something that should be idempotent is posting to create a new VM instance. Which you certainly may do. It's just a funny choice of example since that's the one example where the behavior he describes is potentially expected.
It would be weird if he used a method like GET which is normally idempotent. People already make those be idempotent, so they would miss that the point is that a good API has all idempotent endpoints, POST and not.
