🛒 MicroMart: Enterprise E-Commerce Ecosystem

MicroMart is an enterprise-grade, distributed e-commerce ecosystem built on a reactive, event-driven architecture. Designed for high availability and elastic scalability, the platform demonstrates sophisticated patterns including distributed transactions (Saga), reactive data streams, and automated resilience.

🏆 Roadmap.sh Project: This repository is my official solution for the Scalable E-Commerce Platform architecture challenge.

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🏗️ System Architecture

This ecosystem follows the API Gateway Pattern, Service Discovery Pattern, and the Database-per-Service Pattern to ensure high scalability and loose coupling.

graph LR
    %% Color Styling Definitions
    classDef business fill:#0d6efd,color:#fff,stroke:#0a58ca,stroke-width:2px;
    classDef infra fill:#198754,color:#fff,stroke:#146c43,stroke-width:2px;
    classDef database fill:#ffc107,color:#000,stroke:#cc9a06,stroke-width:2px;
    classDef shared fill:#6f42c1,color:#fff,stroke:#59339d,stroke-width:2px;
    classDef external fill:#ffffff,color:#000,stroke:#cccccc,stroke-width:2px;

    Client((Customer App)) --> Gateway[API Gateway: 7082]
    class Client external
    class Gateway business
    
    subgraph "🟩 Infrastructure"
        Config[Config Server: 7012]
        Eureka[Eureka Discovery: 7010]
        Rabbit[RabbitMQ Broker]
    end
    class Config,Eureka,Rabbit infra

    subgraph "🟦 Business Logic Services"
        Users[Users Service: 0]
        Products[Products Service: 7016]
        Cart[Cart Service: 7041]
        Order[Order Service: 7063]
        Inventory[Inventory Service: 7061]
        Payment[Payment Service: 7007]
        Notification[Notification Service: 7050]
    end
    class Users,Products,Cart,Order,Inventory,Payment,Notification business

    subgraph "🟨 Databases"
        UsersDB[(Users DB)]
        ProductsDB[(Products DB)]
        OrderDB[(Order DB)]
        PaymentDB[(Payment DB)]
        InventoryDB[(Inventory DB)]
    end
    class UsersDB,ProductsDB,OrderDB,PaymentDB,InventoryDB database

    subgraph "🟪 Cross-Cutting Concerns"
        JWT[["📦 JwtAuthorities.jar <br/> (Embedded in Services)"]]
    end
    class JWT shared

    %% Network & Sync Routing
    Gateway -.-> Eureka
    Cart -->|Sync: Check Stock| Inventory
    Order -->|Sync: Request Link| Payment

    %% Async RabbitMQ Flow
    Order -.->|Publishes Event| Rabbit
    Payment -.->|Publishes Event| Rabbit
    Rabbit -.->|Consumes Event| Inventory & Cart & Notification & Order

    %% Database Connections
    Users --> UsersDB
    Products --> ProductsDB
    Order --> OrderDB
    Payment --> PaymentDB
    Inventory --> InventoryDB
    Cart --> OrderDB

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📊 Diagram Legend

Shape & Color	Node Type	Description
⚪ White Circle	External Actor	The end-user client (Mobile/Web App).
🟦 Blue Rectangle	Business Service	Independent microservices handling core domain logic.
🟩 Green Rectangle	Infrastructure	Backbone services supporting the ecosystem (Routing, Messaging).
🟨 Yellow Cylinder	Database	Isolated persistence layers (Database-per-Service pattern).
🟪 Purple Box	Shared Library	Reusable .jar dependencies embedded at compile-time.

Communication Lines:

• ───> Solid Line: Synchronous HTTP/REST Call (Blocking)
• - - -> Dotted Line: Asynchronous Message / Event-Driven Flow (Non-Blocking)

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🔄 The Transaction Lifecycle

When a user places an order, the following distributed transaction occurs across the ecosystem:

sequenceDiagram
    participant User
    participant Gateway
    participant Auth as Users (JWT)
    participant Order
    participant Payment
    participant Rabbit as RabbitMQ (Broker)
    participant Inventory
    participant Notify as Notification

    User->>Gateway: POST /api/v1/orders/checkout
    Gateway->>Auth: Validate JWT Token
    Auth-->>Gateway: Token Valid (Role: USER)
    Gateway->>Order: Create Order #99 (Status: PENDING)
    Order->>Payment: Request Payment Session
    Payment-->>User: Redirect to Payment Gateway
    
    Note over Payment: User completes transaction
    
    Payment->>Rabbit: Publish: PaymentSuccessEvent
    
    par Async Consumers
        Rabbit-->>Order: Update Status to PAID
        Rabbit-->>Inventory: Deduct Stock
        Rabbit-->>Notify: Send Confirmation Email
    end

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🛡️ Resilience & Observability

MicroMart is built with a "Design for Failure" mindset. The API Gateway serves as a resilient entry point using:

• Circuit Breakers (Resilience4J): Configured with a state-machine for high-risk routes (like Users).
  • Trip Logic: If the failure rate hits 50% over a rolling window of 10 calls, the circuit opens to halt traffic.
  • Self-Healing (Half-Open): After a 10-second wait time, the Gateway allows exactly 3 test requests through. If they succeed, the circuit closes and normal traffic resumes; if they fail, it trips open again.
• Time Limiting: Strict 5-second timeouts ensure that a hanging downstream service does not exhaust the Gateway's thread pool.
• Global CORS: Securely configured for modern frontend integration (e.g., React on port 3000).
• Observability: Integrated with Spring Boot Actuator for real-time health checks and metric gathering.

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📦 Service Registry

Service	Primary Responsibility	Port
Gateway	Unified entry point, routing, and load balancing	7082
ConfigServer	Centralized configuration management	7012
EurekaServer	Service registration and dynamic discovery	7010
Users	Identity management and RBAC (Role-Based Access Control)	0
Products	Catalog management and product metadata	7016
Cart	Real-time shopping cart persistence	7041
Order	Transaction orchestration and checkout flow	7063
Inventory	Stock tracking and safety-stock logic	7061
Payment	Transaction processing and billing history	7007
Notification	Multi-channel messaging (Email/SMS) via RabbitMQ	7050
JwtAuthorities	[Library] Reusable security filters and token logic	N/A

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🚀 Local Development Setup

1. Install Shared Library

Because JwtAuthorities is a custom internal library, it must be installed to your local .m2 repository first:

cd JwtAuthorities && mvn clean install

2. Build All Services

mvn clean package -DskipTests

3. Run via Docker Compose

docker-compose up --build