# Building a Three-Tier Architecture on Azure

Introduction Some assignments teach you tools. This one taught me how to think. As part of DMI Cohort 2, I was tasked with deploying the Book Review App — a Next.js frontend, Node.js backend, and MySQL database — in a fully production-style three-tier architecture on Azure. No step-by-step guide. Just the requirements, Azure documentation, and whatever problem-solving I could bring. This post covers what I built, the real challenges I hit, and the mental shift this assignment forced. What Is a Three-Tier Architecture? A three-tier architecture separates an application into three distinct layers: Tier What it does Web Tier Serves the frontend. Handles HTTP requests from users. App Tier Business logic. Processes requests, talks to the database. Database Tier Where the data lives. Never exposed to the internet. Each tier lives in its own subnet with its own security rules: Web tier → can talk to App tier App tier → can talk to Database tier Nothing else This isolation means a breach in on