Kafka Order Processing System (Spring Boot Modularity + Docker)

A modular Spring Boot system demonstrating event-driven architecture using Apache Kafka, with services for order processing and inventory management.

This project showcases how to decouple services using Kafka while maintaining data consistency across modules.

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Architecture Overview

Client → Producer API → Kafka Topic → Consumers
                                      ├── Order Service (DB)
                                      └── Inventory Service (DB)

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Modules

Module	Responsibility
pssdata	Shared DTOs (Order, OrderItem)
producer	Publishes order events to Kafka
consumer	Persists orders into database
inventory	Updates stock based on orders

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Tech Stack

• Java 17
• Spring Boot
• Spring Kafka
• Spring Data JPA
• MySQL
• Docker / Docker Compose

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Key Features

• Event-driven communication using Kafka
• Modular architecture (shared DTO layer)
• Asynchronous processing
• Inventory synchronization
• Transactional database operations
• Dockerized Kafka broker

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Kafka Flow

1. Client sends order → Producer API

2. Producer publishes to pss_order

3. Consumers process event:

   • Order Service → saves order
   • Inventory Service → updates stock

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Running the Project

1. Start Kafka

docker-compose up -d

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2. Run Services

Run each module:

cd producer && mvn spring-boot:run
cd consumer && mvn spring-boot:run
cd inventory && mvn spring-boot:run

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3. Test API

POST /api/v1/kafka/publish

Example payload:

{
  "id": 1,
  "customerName": "Nicko",
  "items": [
    {
      "productId": 1,
      "productName": "Keyboard",
      "quantity": 2,
      "price": 1500
    }
  ]
}

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Project Structure

├── producer/
├── consumer/
├── inventory/
├── pssdata/
├── docker-compose.yml
├── .env.example
├── application-example.yml

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Improvements / Future Work

• Add retry mechanism (Kafka DLQ)
• Introduce schema validation (Avro / Schema Registry)
• Add centralized logging (ELK stack)
• Add API gateway
• Convert to full microservices deployment