01Overview
The Ledger System is a secure financial REST API designed to handle protected account access, fund transfers, and automated transactional notifications. It acts as the backbone for a hypothetical banking or wallet application.
02Architecture & Tech
Built strictly as a backend service using Node.js, Express, and MongoDB. Security is paramount, so all passwords are hashed using bcrypt, and API access is secured via JWT. The core ledger logic is written as a series of modular controllers that validate balances, handle concurrent transfers, and emit events to a notification service that triggers email alerts (via Nodemailer) for transaction confirmations.
03Challenges
Financial systems cannot tolerate errors or partial updates. If a transfer deducts money from User A but fails before crediting User B, the funds are lost. Additionally, validating inputs to prevent negative transfers or overflow attacks was critical.
04Solutions
We utilized MongoDB ACID transactions to ensure that fund transfers are atomic — either the entire transfer succeeds, or the whole operation is rolled back, guaranteeing zero data inconsistency. We also implemented strict input validation middleware (using Joi) to sanitize all incoming requests before they ever touch the database logic.
Role
Backend API Engineer
Impact
enabled secure transfers with automated transactional notifications
Stack
Node.jsExpressMongoDBJWTbcrypt
Key Features
- ◆JWT authentication + bcrypt
- ◆Fund transfer system
- ◆Email notifications
- ◆Transaction history
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