[bkirwi]

Hey, thanks for the excellent writeup.

I enjoyed and totally endorse the content of your blog post, but I did find the title / intro a bit misleading. Exactly-once is pretty much always what people want: it's the easiest model for most folks to reason about, especially when they're new to the whole distributed-systems thing. (If exactly-once delivery was easy, you certainly wouldn't find people going out of their way to build systems that dropped or duplicated messages.) Of course, you might not need exactly-once delivery to get what you want -- which is good, because like you say, that's a hard / impossible problem to solve in general.

It feels to me like people in the stream processing universe have taken that message a bit too much to heart -- things like the 'lambda architecture' treat stream processing as "too hard to get right" and relegate it to approximate, disposable calculations only. My post was partly an effort to push back on this; as a community, I don't think we should give up without a fight.