Understanding Event-Driven Architecture

Event-driven architecture (EDA) is a design pattern that promotes the production, detection, and consumption of events. It's become a cornerstone of modern distributed systems.

What is an Event?

An event represents a significant change in state. For example:

• A user registered
• An order was placed
• A payment was processed

Core Components

Benefits

• Loose coupling: Services don't need to know about each other
• Scalability: Consumers can be scaled independently
• Resilience: If a consumer is down, events are queued
• Flexibility: New consumers can be added without modifying producers

When to Use EDA

Event-driven architecture shines when:

1. You need asynchronous processing
2. Multiple services need to react to the same event
3. You want to build an audit trail of everything that happened
4. You need to decouple services for independent deployment

Implementation with Apache Kafka

@Service
public class OrderEventProducer {

    private final KafkaTemplate<String, OrderEvent> kafkaTemplate;

    public OrderEventProducer(KafkaTemplate<String, OrderEvent> kafkaTemplate) {
        this.kafkaTemplate = kafkaTemplate;
    }

    public void publishOrderCreated(Order order) {
        OrderEvent event = new OrderEvent("ORDER_CREATED", order);
        kafkaTemplate.send("orders", order.getId(), event);
    }
}

Conclusion

Event-driven architecture is a powerful pattern for building scalable, resilient distributed systems. Start with simple pub/sub patterns and evolve as your needs grow.