> An operation is idempotent if performing it multiple times yields the same result as performing it exactly once. And then he casually offers an API that does different things on first and second call as the "good" example. If you have a "create a virtual machine" API it better create a fucking virtual machine. If I call the damn thing twice, I expect to have two VMs. If there is some sort of unique argument like cr…
An advantage of this style is that if the client dies or times out during the (long) operation, it can retry and get the same answer instantly.