Order Management System

Order States

pending -> confirmed -> processing -> shipped -> delivered
  |          |            |            |
  v          v            v            v
cancelled cancelled   cancelled     returned

Scale

• 5K orders/sec peak
• All state changes tracked in audit log
• Search latency p99 < 500ms

Key Points

• Understanding Order Management System is essential for production systems
• Always consider scalability and maintainability
• Test thoroughly before deploying to production
• Monitor performance and set up alerting

Common Patterns

1. Validation: Always validate input at the boundary
2. Error Handling: Use structured error responses
3. Logging: Log key events for debugging
4. Testing: Unit, integration, and load tests
5. Documentation: Keep docs updated with code changes

Event-Driven Architecture

Order Service -> Event Bus -> Payment, Shipping, Notify services

State Machine

• Enforces valid transitions
• Event sourcing for audit trail
• Idempotency keys for duplicate prevention
• Optimistic locking (version field) for concurrency

Event Publishing

@Transactional
public void updateStatus(Long orderId, OrderStatus newStatus) {
  Order order = orderRepository.findById(orderId);
  order.transition(newStatus);
  orderRepository.save(order);
  eventPublisher.publish(new OrderStatusChanged(orderId, newStatus));
}

Tables

• orders(id, user_id, status, version, items JSONB, total, idempotency_key)
• order_events(id, order_id, event_type, payload JSONB)

Optimistic Locking

UPDATE orders SET status = ?, version = version + 1
WHERE id = ? AND version = ?;

Key Points

• Understanding Order Management System is essential for production systems
• Always consider scalability and maintainability
• Test thoroughly before deploying to production
• Monitor performance and set up alerting

Common Patterns

1. Validation: Always validate input at the boundary
2. Error Handling: Use structured error responses
3. Logging: Log key events for debugging
4. Testing: Unit, integration, and load tests
5. Documentation: Keep docs updated with code changes