CQRS

1. The Incident

The orders database serves everyone, and everyone wants something different from it.

Checkout writes orders: it wants a clean, normalized schema with strict validation and transactions, so nothing invalid ever gets in. The orders page reads them: it joins six tables (order, items, customer, addresses, shipments, payments) to render one screen, and that join costs 300 ms. The support team wants to search orders by customer name and product: text search, which the database does badly. Analytics wants daily aggregates. Each team, reasonably, asks for help.