CAPITAL MANAGER (Expense Tracker)

Developed Capital Manager, a full-stack financial tracking application designed to streamline personal expense management. The system was built as a Single Page Application (SPA) supported by an Express backend and a PostgreSQL database, prioritizing data integrity and real-time synchronization.

Architecture & Tech Stack

Frontend (Client-Side)

• Core Framework: Bootstrapped with React (v19.2.5) via Vite, styled with Tailwind CSS, and integrated Chart.js for interactive data visualization.
• State Management: Handled via a Context-based global system (ExpenseContext.jsx), utilizing Promise.all for concurrent API calls to keep UI state consistent after database writes.
• Localization & UI Layers: Implemented UI components, dual-language localization (English and Indonesian), and a privacy masking toggle (Eye/EyeOff) to obscure sensitive financial figures on demand.

Backend Infrastructure & Database

• Server Environment: Built on Node.js and Express (v5.2.1). Deployed as Vercel serverless functions via Express route handlers.
• Database Schema: Designed a normalized PostgreSQL relational database consisting of users, accounts, categories, and transactions tables.
• Data Integrity: Enforced atomic ledger balance updates within SQL transactions (BEGIN ... COMMIT) to ensure consistent wallet-to-wallet transfers and prevent race conditions.

Security Operations

• Authentication: Configured stateless authentication via JSON Web Tokens (JWT), verified against HTTP Authorization headers.
• Cryptography: Implemented password salting and hashing via Node's native crypto.randomBytes(16) and crypto.scryptSync().
• Traffic Control: Built a custom in-memory rate limiter using a Map-based IP tracker that caps requests at 1,000 per 15-minute window per IP to mitigate abuse.

Core Competencies

React, Node.js, Express.js, PostgreSQL, Web Security, State Management, REST API Architecture