Sure, but you said that assigning unique ID's to messages and not executing the same ID twice was a "third option", besides establishing idempotency. I'm saying it's not a "third option", but instead it literally is "establishing idempotency".
I guess we'll just have to agree to disagree about that.
Here is a quote from the original article that supports my position:
"Therefore consumer applications will need to perform deduplication or handle incoming messages in an idempotent manner. ... The way we achieve exactly-once delivery in practice is by faking it. Either the messages themselves should be idempotent, meaning they can be applied more than once without adverse effects, or we remove the need for idempotency through deduplication."
