🏦 Banking Backend Ledger System

A robust, secure, and scalable backend system designed to handle core banking operations. This project implements a reliable ledger system, secure money transfers with idempotency, and comprehensive API documentation.

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🚀 Key Features

• 🔐 Secure Authentication: Multi-layered security using JWT (JSON Web Tokens) and Bcrypt for password hashing.
• 📊 Double-Entry Ledger: Every transaction is recorded as a linked Debit and Credit entry, ensuring accounting integrity.
• ⚡ Atomic Transactions: Utilizes MongoDB Sessions/Transactions to ensure that money transfers either succeed completely or fail gracefully (ACID compliance).
• 🛡️ Idempotency: Built-in protection against duplicate transactions using unique idempotency keys.
• 📧 Automated Notifications: Integrated email service to notify users of successful transactions.
• 🔒 Security First: implementation of Helmet for HTTP headers, Morgan for logging, and Rate Limiting to prevent brute-force attacks.
• 📖 Live API Documentation: Fully interactive Swagger documentation for seamless API testing.

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🛠️ Tech Stack

• Runtime: Node.js
• Framework: Express.js
• Database: MongoDB (Mongoose ORM)
• Documentation: Swagger UI & Swagger JSDoc
• Security: JWT, Bcrypt, Helmet, Express-Rate-Limit
• Logging: Morgan
• Deployment Ready: Optimized for platforms like Render

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📖 API Documentation (Swagger)

The API is fully documented using Swagger. You can explore and test all endpoints directly from the browser.

🌐 Live Production Link

Access the API docs here: Live Documentation

💻 Local Development

If running locally, access the docs at: http://localhost:3000/api-docs

Note: In the Swagger UI, use the Servers dropdown at the top to switch between the Localhost and Production environments.

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📂 Project Structure

├── src
│   ├── config         # Database and Swagger configurations
│   ├── controllers    # Business logic for Auth, Accounts, and Transactions
│   ├── middlewares    # Auth guards and request limiters
│   ├── models         # Mongoose schemas (User, Account, Transaction, Ledger)
│   ├── routes         # API route definitions
│   ├── services       # Email and other third-party integrations
│   └── app.js         # Express app initialization
├── server.js          # Entry point of the application
└── .env               # Environment variables

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⚙️ Installation & Setup

1. Clone the repository:

   git clone https://github.com/pKm720/Banking-Backend-Ledger.git
   cd Banking-Backend-Ledger

2. Install dependencies:

   npm install

3. Configure Environment Variables: Create a .env file in the root directory and add the following:

   MONGO_URL=your_mongodb_connection_string
   JWT_SEC=your_secret_key
   EMAIL_USER=your_email@gmail.com
   APP_PASSWORD=your_app_password
   NODE_ENV=development
   PORT_ENV=3000

4. Run the server:

   npm start

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🏗️ How It Works (The Core Logic)

The Ledger System

Unlike simple balance updates, this system uses a Ledger Model. When User A sends money to User B:

1. A Transaction is created with a PENDING status.
2. A DEBIT entry is created for User A.
3. A CREDIT entry is created for User B.
4. The Transaction status is updated to COMPLETED.
5. All these steps are wrapped in a Mongoose Session—if any step fails, the entire operation is rolled back.

Idempotency

To prevent accidental double-spending (e.g., if a user clicks "Send" twice), every transaction requires an idempotencyKey. The system checks if a transaction with that key already exists before processing.

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👨‍💻 About the Author

I am a passionate Developer focused on building secure and high-performance financial systems. This project demonstrates my ability to handle complex database operations, implement security best practices, and deliver professional-grade documentation.

Looking for a dedicated developer for your team? Let's connect!

• GitHub: pKm720
• LinkedIn: Priyanshu Mahato

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Created with ❤️ for a secure financial future.