Event-Driven Architecture¶

Category: Architecture Tags: event-driven, kafka, java, kubernetes, microservices

Overview¶

Event-Driven Architecture (EDA) is a design paradigm where components communicate through events—emitted, consumed, and reacted upon—decoupling the services.

What It Is¶

Asynchronous communication – Producers emit events, consumers listen and act
Loose coupling – Services do not directly call each other
High scalability – Suits high-throughput and reactive systems

Why Use It¶

Enables real-time processing and responsiveness
Decouples services for better fault tolerance
Facilitates audit trails and logging through events

When To Use It¶

Real-time systems (e.g. fraud detection, analytics)
Microservices needing loose coupling
Need for async workflows and horizontal scaling

Implementation Examples¶

Code Example (Java + Spring Kafka)¶

@Component
public class OrderListener {
    @KafkaListener(topics = "orders")
    public void handleOrder(String orderJson) {
        // process order
    }
}

Infra Example (Kubernetes + Kafka)¶

apiVersion: apps/v1
kind: Deployment
metadata:
  name: kafka-consumer
spec:
  replicas: 2
  selector:
    matchLabels:
      app: kafka-consumer
  template:
    metadata:
      labels:
        app: kafka-consumer
    spec:
      containers:
      - name: consumer
        image: myregistry/kafka-consumer:latest
        env:
        - name: KAFKA_BOOTSTRAP_SERVERS
          value: kafka:9092

Key Concepts Summary¶

Events decouple producers and consumers
Supports async flows, retry patterns
Event brokers like Kafka or RabbitMQ act as middleware

Best Practices / Tips¶

Design events as immutable facts
Use schema validation (e.g., Avro)
Handle idempotency in consumers

Common Issues / Troubleshooting¶

Problem 1: Event loss or duplication¶

Cause: Consumer restarts or network partition
Solution: Use offset management and idempotent processing

Problem 2: Hard to trace event flow¶

Cause: No centralized logging or monitoring
Solution: Use distributed tracing and observability tools

References / Further Reading¶

https://martinfowler.com/articles/201701-event-driven.html
https://kafka.apache.org/documentation/