Fintech Module · 2026
Financial Transaction Module
Wallet, payment gateway, and transaction management system
Overview
A full-featured financial module built for an internal platform, handling wallets, deposits, withdrawals, payment gateway integration, and complete transaction history. Secured with JWT authentication and role-based access control.
Architecture
RESTful API built with Express.js and TypeScript, deployed on a Linux server managed via Nginx and PM2. CI/CD is automated through GitHub Actions. Data is persisted in MongoDB (for flexible transaction metadata) and MySQL (for relational financial records).
Role
Programmer
Year
2026
Tech Stack
Features
Wallet & Transaction Engine
Handles deposits, withdrawals, and balance tracking with transactional integrity to prevent double-spending or inconsistent states.
Payment Gateway Integration
Seamlessly integrated third-party payment gateways with webhook handling for real-time transaction status updates.
Secure API with JWT & RBAC
All endpoints are secured using JWT tokens, cookie-based sessions, and middleware-enforced role-based access control.
Challenges
Ensuring transaction atomicity across services
Financial operations across wallets and payment gateways had to be atomic. Implemented transactional patterns with rollback logic and idempotency keys to prevent duplicate charges.
Webhook reliability for payment status
Payment gateway webhooks could arrive out of order or fail. Built a retry-safe webhook handler that reconciles payment status from the gateway API when needed.
Results
Deposit, Withdrawal, Transfer
Transaction types
Linux + Nginx + PM2 + CI/CD
Deployment
Lessons Learned
- Idempotency is not optional in financial systems — every mutation endpoint must be safe to call twice.
- Separating the webhook handler from the core transaction logic makes the system more resilient to third-party gateway outages.