This project is a secure web-based wallet application designed to simulate real-world digital payment platforms. The system allows users to register, create a wallet automatically, add money through UPI integration, and perform wallet-based payments while maintaining financial integrity through a ledger-based transaction model.
The application is built with a backend-first architecture where all financial operations are verified and processed server-side. Instead of acting as a banking system, the platform functions as a stored-value wallet layer that records every credit and debit as an immutable transaction. This approach ensures consistency, auditability, and protection against duplicate or partial payment processing.
The project demonstrates how modern wallet systems integrate authentication, payment gateway interaction, database transactions, and cybersecurity principles into a cohesive platform. It emphasizes backend verification, idempotent payment handling, and separation between payment lifecycle tracking and wallet ledger updates.
⭐ Features
User registration and authentication
Automatic wallet creation per user
Wallet balance management
Add money via UPI payment gateway
Wallet-based payments
Ledger-based transaction tracking
Payment lifecycle management (payment attempts)
Idempotent payment handling
Backend-only payment verification
Secure MySQL schema with ACID transactions
🧠 Architecture Highlights
Users → Identity layer
Wallets → Stored value layer
Payment Attempts → External payment lifecycle
Transactions → Immutable financial ledger
This layered architecture mirrors real fintech wallet systems.
🔐 Security Highlights
Password hashing
Backend payment verification via webhooks
Idempotency keys to prevent duplicate credits
Database transaction safety
Separation of wallet state and ledger
Input validation and secure API design
🎯 Learning Goals
Backend system design for fintech applications
Payment lifecycle handling
Ledger-based wallet architecture
MySQL transactional integrity
Secure API development
Idempotent processing design
⭐ Tech Stack
Node.js
Express
MySQL
UPI Payment Gateway (conceptual integration)
REST APIs
🚀 Status
Active development — building backend-first wallet architecture.