Example data. Fieldnote is a fictional company used to fill every board, so the examples tell one consistent story.
Fieldnote, three hours on a wall with Karim, Tom, Ana, Julien and Marc the dispatcher, mapping one intervention from dispatch to invoice.
What the team took away
The free-text parts policy was written years ago as a convenience. On the wall it turned out to be where the 6 % of lost billable parts goes, and nobody in the room had connected the two before.
How to run it
Preparation
Get a wall, not a table. Event storming needs eight metres of paper roll and room for fifteen people to stand and move.
Buy far more orange stickies than you think. Running out of orange mid-session stops the only thing that matters.
Invite at least one person who knows the business rules and has been there for years. Without them the timeline stops at what the code does.
Agree the colour legend before starting and post it: orange for events, blue for commands, yellow for actors, purple for policies, pink for hot spots.
Agenda
40 min
Chaotic exploration Everyone writes domain events on orange stickies, in the past tense, and puts them on the wall anywhere. No order, no discussion, no filtering. The mess is the point: it shows the real surface of the domain.
40 min
Enforce the timeline Together, push the events left to right in time order. Duplicates merge, gaps appear, and arguments start. Every argument gets a pink sticky rather than a resolution.
35 min
Commands and actors For each event, what triggered it and who did it. Blue command, yellow actor. Events with no trigger are usually the ones nobody understood.
30 min
Policies and read models Whenever an event automatically causes another, name the rule. These policies are where product decisions hide inside what looks like technical behaviour.
35 min
Walk the hot spots Go through every pink sticky out loud. Assign each one an owner and a next step: a decision to make, a person to ask, or a spike to run.
Pitfalls
Letting engineers turn it into a system design session. The wall describes what happens in the business, not what the code does. Keep asking 'and then what happened for the customer'.
Cleaning up too early. If you enforce the timeline in the first twenty minutes, you get the model people already agreed on, which is the one you already had.
Resolving hot spots on the spot. A pink sticky is worth more than a rushed decision made by whoever spoke loudest. Park it and move.
Afterwards
The timeline feeds a story map or a service blueprint directly. The hot spots are the best backlog of discovery work you will get in one session.