Event-Driven Architecture Patterns

# Event-Driven Architecture Patterns

Event-driven architectures enable loose coupling and scalability. Here's how to implement them effectively.

## Core Concepts

**Events vs Commands**

Events describe what happened. Commands tell something to happen. Know the difference.

**Event Sourcing**

Store all changes as a sequence of events. This provides a complete audit trail and enables powerful replay capabilities.

## Messaging Patterns

**Pub/Sub**

Publishers emit events; subscribers consume them. Great for fan-out scenarios.

**Message Queues**

Point-to-point messaging with guaranteed delivery. Use for work distribution.

## Challenges

- Eventual consistency

- Message ordering

- Duplicate handling

- Error recovery

**Tools**: Kafka, RabbitMQ, AWS SNS/SQS, Google Pub/Sub

Events enable systems to evolve independently and scale effortlessly.