Live session L04 · day 20

At-least-once is not a guarantee you get. It is a bill you pay at every sink

One event, three consumer groups, three definitions of done. Demonstrated by breaking it.

Releases Monday, 19 October 2026

What it covers

The outbox is fifteen lines and everyone writes about it. The hard part is three consumers who each have a different answer to seeing the same event twice.

What breaks

Kill a consumer mid-flight. Show the duplicate arrive. Three sinks still agree. Every session breaks something on purpose. A build that only ever works is a demo, and a demo is the one thing this is not.

Afterwards

The recording is posted on this page, and the write-up goes out the same day at designsbyduhart.org/blog.