Booking Lifecycle under Event Sourcing Diagram

Events in Past Tense

SEAT_BOOKED and SEAT_CANCELED record facts that happened
A cancellation never erases the earlier booking fact
Each transition is one immutable event in the log

Never Mutate

Mistakes are fixed by new compensating events
The log keeps the full history: a built-in audit trail
Fewer irreversible actions means easier evolution

Views Follow the Log

Every event updates the materialized views
Delete a view and replay the same events to rebuild it
A view bug is fixed by new code, not by patching data

Order Matters

Processing events out of order produces nonsense
Unlike a fact table, the sequence carries meaning
All consumers must see the same event order