ORDER · Critical priority
Checkout + orders
Authoritative producer for order acceptance and lifecycle state. Checkout validates the offer and the order service commits headers, items, discounts, taxes, status, and fulfillment intent before publishing.
Amazon example
One checkout creates order ORD-123 with three order items from two sellers. A later cancellation affects only one item, so item and order transitions remain separate facts.
Event grain
One immutable lifecycle transition per order or order item. Current order state is a projection, not a replacement for event history.
Capture behavior
Transactional outbox for business events plus table CDC for audit, recovery, and legacy fields. Publish only after the owned state commits.
Contract + ordering
Key order topics by order_id; carry order_item_id where applicable, source_sequence_number, amounts in minor units, currency, promotion version, and status reason.
Downstream use
Customer service, order health, seller operations, fulfillment, finance, demand, conversion, and certified order-item facts.
Source authority
Only the order domain declares placed, cancelled, or closed. A client purchase event is behavioral evidence, not an accepted order.