Event-Driven Microservices

Order processing system using event-driven architecture with Kafka, CQRS pattern, and Go microservices.

Features

• Event-driven communication via Apache Kafka
• CQRS (Command Query Responsibility Segregation)
• Saga pattern for distributed transactions
• Multiple microservices: Order, Payment, Inventory, Notification
• Event sourcing with replay capability
• Health checks and graceful shutdown

Tech Stack

Component	Technology
Services	Go
Messaging	Apache Kafka
Databases	PostgreSQL (per service)
Containerization	Docker, Docker Compose
API Gateway	NGINX

Architecture

┌───────────┐   ┌───────────────────────────────────┐
│  Client   │──▶│           API Gateway              │
└───────────┘   └──────┬────────────┬────────────────┘
                       │            │
              ┌────────▼──┐  ┌─────▼────────┐
              │  Order    │  │  Query       │
              │  Service  │  │  Service     │
              └─────┬─────┘  └──────────────┘
                    │ publish
              ┌─────▼─────┐
              │   Kafka   │
              └──┬──┬──┬──┘
        consume  │  │  │
     ┌───────────┘  │  └───────────┐
     │              │              │
┌────▼─────┐ ┌─────▼────┐ ┌──────▼────────┐
│ Payment  │ │Inventory │ │ Notification  │
│ Service  │ │ Service  │ │ Service       │
└──────────┘ └──────────┘ └───────────────┘

Services

Service	Port	Responsibility
Order	8081	Create/manage orders
Payment	8082	Process payments
Inventory	8083	Stock management
Notification	8084	Email/SMS alerts
Query	8085	Read-optimized queries (CQRS)

Kafka Topics

Topic	Producer	Consumers
order.created	Order	Payment, Inventory
payment.processed	Payment	Order, Notification
inventory.reserved	Inventory	Order
order.completed	Order	Notification, Query

Getting Started

docker-compose up
# Order API at http://localhost:8081

Roadmap

• Project setup
• Kafka + Zookeeper Docker setup
• Order service with event publishing
• Payment service consumer
• Inventory service consumer
• Notification service
• CQRS query service
• Saga pattern implementation
• Health checks
• Integration tests

License

MIT