Distributed Event-Driven Order & Analytics Platform

A production-ready microservices platform demonstrating event-driven architecture, asynchronous communication, and distributed systems design patterns using Spring Boot, Apache Kafka, and PostgreSQL.

Architecture

Client → Order Service → Kafka → Inventory Service
            ↓                        ↓
        PostgreSQL              PostgreSQL

Features

• Event-Driven Architecture: Asynchronous communication via Apache Kafka
• Microservices: Independently deployable services with separate databases
• RESTful APIs: Clean, well-documented endpoints
• Transaction Management: ACID compliance with Spring @Transactional
• Docker Support: Containerized infrastructure (Kafka, Zookeeper, PostgreSQL)
• Database-Per-Service Pattern: Service autonomy and fault isolation

Tech Stack

• Backend: Java 17+, Spring Boot 3.4.0
• Messaging: Apache Kafka 7.4.0
• Database: PostgreSQL 18
• ORM: Spring Data JPA (Hibernate)
• Build Tool: Maven
• Containerization: Docker & Docker Compose

Prerequisites

• JDK 17 or higher
• Docker Desktop
• Maven 3.6+
• PostgreSQL 18 (or use Docker)

Quick Start

1. Start Infrastructure

docker-compose up -d

2. Run Order Service

cd order-service
mvn spring-boot:run

3. Run Inventory Service

cd inventory-service
mvn spring-boot:run

4. Test the System

# Create an order
curl -X POST http://localhost:8080/api/orders \
  -H "Content-Type: application/json" \
  -d '{
    "customerId": "CUST001",
    "productId": "PROD123",
    "quantity": 5,
    "totalPrice": 249.99
  }'

# Check inventory
curl http://localhost:8081/api/inventory/PROD123

API Endpoints

Order Service (Port 8080)

• POST /api/orders - Create new order
• GET /api/orders - Get all orders
• GET /api/orders/{id} - Get order by ID
• GET /api/orders/customer/{customerId} - Get orders by customer
• PATCH /api/orders/{id}/status?status=CONFIRMED - Update order status

Inventory Service (Port 8081)

• GET /api/inventory/{productId} - Get inventory for product
• GET /api/inventory - Get all inventory
• POST /api/inventory?productId=X&initialStock=100 - Create inventory

Event Flow

1. Client sends POST request to Order Service
2. Order Service persists order to PostgreSQL
3. Order Service publishes ORDER_CREATED event to Kafka topic order.events
4. Inventory Service consumes event from Kafka
5. Inventory Service updates inventory in its PostgreSQL database

Monitoring Kafka

# List topics
docker exec -it kafka kafka-topics --list --bootstrap-server localhost:9092

# View messages
docker exec -it kafka kafka-console-consumer \
  --bootstrap-server localhost:9092 \
  --topic order.events \
  --from-beginning

# Check consumer groups
docker exec -it kafka kafka-consumer-groups \
  --bootstrap-server localhost:9092 \
  --describe \
  --group inventory-service-group

Testing

# Run tests
mvn test

# Build
mvn clean install

License

MIT

Author

Ayush Pathak

Contributing

Contributions welcome! Please open an issue or PR.