[gmcquistin]

> the receiver can easily check if a specific message was already received

It seems like you're conflating exactly-once delivery with exactly-once processing. Your proposed solution is only necessary _because_ we can't have exactly-once delivery as TFA states.

[jongjong]

I don't agree with that contrived definition of delivery. As a developer, what I care about is delivery of the message to my function/handler. E.g. so that I can store it in my local database/store on the receiver side exactly once and ultimately show it to the user exactly once. Definitely possible.