Event-Driven Architecture Patterns
In a microservices architecture, services often need to react to changes happening elsewhere in the system. For example, consider an e-commerce application. When a customer completes a payment, several things might need to happen:
- The Order Service updates the order status.
- The Inventory Service confirms the inventory reservation.
- The Notification Service sends a payment confirmation.
- The Analytics Service updates revenue metrics.
One approach is for the Payment Service to call each of these services directly. However, this creates dependencies. The Payment Service needs to know which services exist, how to communicate with them, and how to handle their failures.
An alternative is to publish an event indicating that the payment has been completed. Other services can independently react to that event. This is the foundation of Event-Driven Architecture (EDA).
But event-driven architecture is not a single design pattern. It includes several patterns for publishing events, distributing information, coordinating workflows, and maintaining consistent data across services. Let's explore the most important patterns and understand when to use them.