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Engineered a High-Integrity Paper Trading & Portfolio Engine (Node.js, Express & PostgreSQL/Prisma)
Project Overview:
I built a full-fledged mock trading and portfolio management backend designed to handle real-world financial transaction logic. The core focus here wasn't just basic CRUD, but ensuring bulletproof data integrity, atomic trade executions, and dynamic portfolio tracking.
The Problem & Architecture:
In financial apps, handling concurrent balance deductions and asset allocations can lead to race conditions or data mismatches if not handled properly. I designed this system with database-level constraints and atomic transaction rollbacks using Prisma ORM with PostgreSQL.
What I Built & Implemented:
Atomic Buy/Sell Execution Engine:
Trade operations are wrapped inside database transactions ($transaction). When a user buys an asset, the wallet deduction, transaction logging, and weighted average price (avgPrice) holding updates happen as a single atomic unit. If anything fails, it rolls back cleanly.
Live Portfolio & PnL Engine:
Built a centralized portfolio summarizer that calculates real-time holding valuations, total invested capital, unrealized profit/loss, and total net worth dynamically based on live asset prices.
Secure Authentication & Access Control:
Implemented stateless JWT-based authentication with bcrypt password hashing to secure trading routes and ensure user-specific asset privacy.
Notification & Activity Stream:
Created an integrated notification system that triggers real-time alerts whenever trades execute, keeping the user updated on balance credits/debits.
Database Design & Indexing:
PostgreSQL schema optimized with compound unique indexes (e.g., userId_assetName) to prevent duplicate holding records and ensure lightning-fast lookups.
Tech Stack Used:
Backend: Node.js, Express.js
Database & ORM: PostgreSQL, Prisma ORM
Security & Auth: JWT (JSON Web Tokens), Bcrypt
Architecture: MVC Pattern, Modular Routing, RESTful APIs
Next Iterations / In Progress:
Adding WebSocket-based live price streaming and a global leaderboard to rank traders by total net worth.
Feel free to reach out if you're looking for a backend developer who can build scalable, transaction-safe APIs and robust architectures!
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