🧩 Spring Boot Microservices Architecture Practice

Below this readme has:

• Overview (short explanation of the project)
• Tech Stack (used technologies)
• Architecture Concepts (used architecture concepts)
• Project Structure (how the project is structured folder wise)
• Architecture Flow (how does everything work together)
• Services (each service's explanation)

📌 Overview

This repository contains a ecommerce microservices architecture practice project build with Spring boot and Angular. It contains of 6 microservices: product-service, order-service, inventory-service, notification-service, api-gateway, frontend.

Goal

This project is intended for learning, experimentation, and portfolio demonstration.

The main purpose of this project is to gain hands-on experience with everything in the "Tech Stack" and "Architecture Concepts" sections.

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🛠 Tech Stack

[NOTE] check out refactor/feign-to-http-interface branch to see the refactored code its a more modern and recommended way to handle inter-service communication in Spring Boot

Backend

• Java 21
• Spring Boot 4 _{(Spring Web, Spring Data JPA, Lombok)}
• Spring Cloud Gateway MVC _{(API Gateway)}
• Spring Cloud Eureka _{(Service Discovery)}
• Spring Cloud OpenFeign _{(REST Client)} (refactored in branch refactor/feign-to-http-interface)
• Resilience4j _{(Circuit Breaker & Retries)}
• Flyway _{(Database Migrations)}
• Swagger (OpenAPI) v3 _{(API Documentation)}

Databases

• MongoDB
• MySQL
• PostgreSQL

Messaging

• Apache Kafka (Kraft) _{(Event-Driven Messaging)}

Observability (Grafana Stack)

• Prometheus _(Metrics)
• Grafana _(Dashboards)
• Loki _{(Log Aggregation)}
• Tempo _{(Distributed Tracing)}

Infrastructure

• Docker
• Kubernetes

Security

• OAuth2
• Keycloak (uses PostgreSQL)

Testing

• JUnit
• Testcontainers
• WireMock

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🧠 Architecture Concepts

This project demonstrates several distributed system patterns and modern engineering practices:

• Microservices Architecture
• Service Discovery _{(Dynamic registration and lookup via Eureka)}
• API Gateway Pattern
• Inter-Service Communication _{(Synchronous via Feign & Asynchronous via Kafka)}
• Centralized Security _{(Auth integration via Keycloak & OAuth2)}
• Event-Driven Architecture _{(Asynchronous processing using Kafka)}
• Resilience Patterns _{(Fault tolerance via Resilience4j)}
• Observability _{(Centralized logs, metrics, and tracing)}
• Database per Service
• Centralized API Docs _{(Gateway-level aggregation)}
• Containerization
• Integration Testing _{(Automated tests with WireMock and Testcontainers)}

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📦 Project Structure

springboot-microservices-ecommerce
│
├── api-gateway
├── product-service
├── order-service
├── inventory-service
├── notification-service
│
├── frontend (might or might not be added later)
│
├── eureka-server
├── docker
└── k8s 

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⚙️ Architecture Flow

🚧 will be added later

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🔧 Services

API Gateway

Responsibilities:

• routing requests to backend services
• centralized security
• centralized api documentation

Technology:

• Spring Cloud Gateway MVC
• Keycloak
• Docker
• Swagger
• Grafana Stack (Prometheus, Grafana, Loki, Tempo)

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Eureka Server

Responsibilities:

• service discovery, finds location of services

Technology:

• Spring Cloud Eureka

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Product Service

Responsibilities:

• create products
• list products

Endpoints:

• POST /api/products createProduct
• GET /api/products getAllProducts

Technology:

• MongoDB
• Docker
• Swagger
• Grafana Stack (Prometheus, Grafana, Loki, Tempo)

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Order Service

Responsibilities:

• create orders

Endpoint:

• POST /api/orders placeOrder

Technology:

• MySQL
• Docker
• Feign Client (for GET /api/inventories)
• Flyway
• Swagger
• Kafka
• Grafana Stack (Prometheus, Grafana, Loki, Tempo)

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Inventory Service

Responsibilities:

• check if products are in stock

Endpoint:

• GET /api/inventories isInStock

Technology:

• MySQL
• Docker
• Flyway
• Swagger
• Grafana Stack (Prometheus, Grafana, Loki, Tempo)

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Notification Service

Responsibilities: -send notifications to users (everytime when order is placed)

Technologies:

• Kafka
• Spring Email
• Grafana Stack (Prometheus, Grafana, Loki, Tempo)

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Frontend(might or might not be added later)

Technologies:

• Angular