🛒 Spring Boot Microservices E‑Commerce Platform

A production‑style Microservices Architecture built using Spring Boot + Angular, demonstrating real‑world backend design including API Gateway security, Keycloak authentication, Kafka event‑driven communication, Resilience4j fault tolerance, and polyglot persistence with MySQL & MongoDB.

---

🚀 Project Overview

This project simulates a scalable e‑commerce backend where multiple independent services communicate through both synchronous and asynchronous mechanisms.

It was built to gain hands‑on experience with distributed systems, secure microservices, and containerized deployment.

---

🧩 Architecture

                        Angular Frontend
                              ↓
                         API Gateway
                              ↓
           ┌──────────────┬──────────────┬──────────────┐
           | Product      | Inventory    | Order        |
           | Service      | Service      | Service      |
           | (MongoDB)    | (MySQL)      | (MySQL)      |
           └──────────────┴──────────────┴──────────────┘
                                ↓
                              Kafka
                                ↓
                       Notification Service

---

🛠️ Tech Stack

Backend

• Java Spring Boot – Microservices development
• Spring Cloud Gateway – API Gateway & routing
• Keycloak – Authentication & Authorization (OAuth2 / OpenID Connect)
• Resilience4j – Circuit Breaker, Retry, Fault tolerance
• Apache Kafka – Event‑driven asynchronous communication

Frontend

• Angular – UI and client‑side interaction

Databases

• MySQL – Order & Inventory Services (transactional data)
• MongoDB – Product Service (flexible catalog data)

DevOps

• Docker & Docker Compose – Multi‑container deployment
• Environment‑based configuration
• Ready for Kubernetes deployment

---

🧩 Microservices Details

1️⃣ Product Service

• Stores product catalog
• Uses MongoDB for flexible schema
• CRUD operations for products

2️⃣ Inventory Service

• Tracks product stock levels
• Uses MySQL for transactional integrity
• Validates stock before order placement

3️⃣ Order Service

• Handles order creation & management
• Uses MySQL database
• Communicates with Inventory Service synchronously
• Publishes Kafka events after order confirmation

4️⃣ Notification Service

• Consumes Kafka events
• Sends order confirmation notifications
• Demonstrates async microservice workflow

5️⃣ API Gateway

• Central entry point
• Request routing
• Security enforcement
• Token validation using Keycloak

---

🔐 Authentication & Authorization

Implemented using Keycloak:

• OAuth2 / OpenID Connect
• Token‑based authentication
• Secure API Gateway routing

---

🔄 Communication Patterns

✔ Synchronous Communication

Order Service → Inventory Service

• Implemented using REST APIs
• Fault tolerance with Resilience4j
• Circuit Breaker + Retry pattern

✔ Asynchronous Communication

Order Service → Notification Service

• Implemented using Apache Kafka
• Event‑driven architecture
• Improved scalability & decoupling

---

📂 Folder Structure

root
 ├── api-gateway
 ├── product-service
 ├── inventory-service
 ├── order-service
 ├── notification-service
 ├── angular-frontend
 └── README.md

---

📌 Key Learnings

• Designing scalable microservices architecture
• Implementing centralized authentication using Keycloak
• Handling service failures with Resilience4j
• Event‑driven architecture using Kafka
• Managing multiple databases in distributed systems
• Containerizing microservices with Docker

---

⭐ Future Improvements

• Kubernetes deployment
• Distributed tracing (Zipkin / Jaeger)
• Centralized logging (ELK / Loki)
• CI/CD pipeline integration
• API rate limiting
• Service discovery (Eureka / Consul)

---

Adarsh Raj If you like this project, give it a ⭐ on GitHub!