Building a Production-Grade Pizza Delivery App — My OIBSIP Level 3 Experience

"Not recommended for beginners." That's what the task sheet said about Level 3 of the Oasis Infobyte Web Development & Design internship. Naturally, that's the one I picked. The Task Level 3 has exactly one task — build a full-stack Pizza Delivery Application. Not a landing page, not a CRUD demo. A real platform: user authentication with email verification, a custom pizza builder, live payments, inventory management, an admin system, and real-time order tracking. The Stack React + Vite + Tailwind on the frontend, Node.js + Express on the backend, MongoDB Atlas for the database, Socket.IO for real-time updates, Razorpay for payments. Deployed across Vercel (frontend) and Railway (backend). What I Built The user journey: register → verify email (Nodemailer) → log in (JWT) → build a pizza in 4 steps (base, sauce, cheese, veggies) with dynamic pricing → pay through Razorpay's checkout → track the order live on a progress bar. The admin side: a separate authenticated dashboard managing a 20-item inventory with low-stock indicators and inline editing, plus order status management. When an admin updates an order's status, the customer's screen updates instantly — no refresh — via Socket.IO rooms per order. Behind the scenes: stock auto-decrements on every successful payment, a node-cron job emails hourly low-stock alerts, and Razorpay payments are verified server-side with HMAC-SHA256 signatures — never trusting the client. What Actually Taught Me Things The features were the syllabus. The debugging was the education. MongoDB Atlas DNS failures — my local machine couldn't resolve mongodb+srv:// connection strings because a VPN was interfering with DNS SRV lookups. Solution: the legacy non-SRV connection string format. Lesson: know what your connection string actually does. Railway's SMTP block — my deployed backend couldn't send verification emails because Railway's free tier blocks outbound SMTP ports entirely. No code fixes this — it's a platform-level restriction. I doc