Rahul Singh

Computer Science graduate with hands-on experience building and shipping full-stack applications using JavaScript, TypeScript, React, Next.js, Node.js, and PostgreSQL. Built production features end-to-end including REST APIs, database systems, payments, authentication, and concurrency-safe workflows. Strong DSA foundation with 200+ problems solved, plus hands-on experience building AI-integrated applications.

Freelance Full-Stack Developer at Chitkara Diagnostics Lab (2026-01 – 2026-03)

• Built and shipped a production healthcare application as the sole engineer, owning PostgreSQL schema design, backend REST APIs, Razorpay integration, and a React-based patient booking workflow supporting daily bookings.
• Implemented a 3-state payment lifecycle with idempotent Razorpay webhook processing, validating payment state before database writes to prevent duplicate confirmations under concurrent requests.
• Eliminated appointment double-booking using PostgreSQL transactions and row-level locking, ensuring consistent slot allocation during simultaneous booking requests; validated critical flows through integration tests.
• Delivered real-time slot availability, secure online payments, appointment history, and live payment-status updates synchronized with backend payment state transitions.

B.Tech in Computer Science Engineering – Jamia Hamdard University (2022-26)