🧩 System Design Lab – API Documentation

This project demonstrates a production-style microservices system design using Spring Boot, API Gateway, JWT security, Kafka, Resilience patterns, and Analytics.

All external traffic flows through the API Gateway, which handles:

• Authentication (JWT)
• Rate limiting
• Request routing
• Security enforcement

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🏗️ Architecture Overview

Services involved:

• API Gateway (8080)
• Auth Service (8086)
• Catalog Service (8081)
• Order Service (8082)
• Payment Service (8084)
• Analytics Service (8085)

Key design patterns implemented:

• API Gateway
• JWT Authentication
• Saga (event-driven)
• Circuit Breaker
• Rate Limiting
• Idempotency
• Event-driven analytics

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🔐 Authentication

Generate JWT Token (via API Gateway)

Endpoint

POST /auth/login

URL

http://localhost:8080/auth/login

Request Body

{
  "username": "chiranjib",
  "password": "password"
}

Response

{
  "token": "<JWT_TOKEN>"
}

Use this token in the Authorization header for all secured APIs:

Authorization: Bearer <JWT_TOKEN>

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🛍️ Catalog APIs

Get Product (via API Gateway – Secured)

GET /catalog/api/products/{id}

Example:

http://localhost:8080/catalog/api/products/1

Headers:

Authorization: Bearer <JWT_TOKEN>

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Create Product (via API Gateway – Secured)

POST /catalog/api/products

Body:

{
  "name": "iPhone 15",
  "category": "Mobile",
  "price": 80000
}

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📦 Order APIs

Place Order (Secured + Idempotent)

POST /orders/api/orders?userId=2&amount=102

Headers:

Authorization: Bearer <JWT_TOKEN>
Idempotency-Key: user-138

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Place Order (Circuit Breaker Demo)

POST /orders/api/orders/{orderId}

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💳 Payment APIs

POST /payments/api/payments?orderId=2&amount=1200.0

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📊 Analytics APIs

GET /analytics/api/analytics/orders
GET /analytics/api/analytics/payments

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🧠 System Design Concepts Demonstrated

• Microservices Architecture
• API Gateway Pattern
• JWT Authentication & Authorization
• Rate Limiting (Redis)
• Idempotency
• Saga Pattern
• Circuit Breaker (Resilience4j)
• Retry & Timeout
• Event-driven Analytics

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🚀 How to Run

docker compose build
docker compose up

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