Building a 3-Tier Web Application on Azure with App Service, Functions, and Cosmos DB

Azure provides a comprehensive suite of cloud services for building modern, scalable web applications. A 3-tier architecture separates applications into three logical layers: the presentation layer (frontend), the application layer (backend API), and the data layer (database). This architectural pattern promotes separation of concerns, making applications easier to develop, maintain, and scale. Azure App Service hosts web applications with built-in scaling and deployment features, Azure Functions provides serverless compute for running backend code without managing infrastructure, and Azure Cosmos DB offers globally distributed NoSQL database capabilities with guaranteed low latency and high availability.

In this lab, you will build a complete 3-tier web application for managing restaurant menu items. You'll deploy Azure infrastructure including App Service, Function App, and Cosmos DB, implement a serverless REST API using Azure Functions with Cosmos DB bindings, create a responsive web frontend with HTML, CSS, and JavaScript, configure cross-origin resource sharing (CORS) for secure communication, and test the complete application with create, read, and update operations.

Objectives

Upon completion of this intermediate level lab, you will be able to:

• Deploy Azure App Service, Azure Functions, and Cosmos DB infrastructure for a 3-tier application
• Implement HTTP-triggered Azure Functions with Cosmos DB input and output bindings
• Configure environment variables and connection strings for cloud applications
• Build a responsive web frontend using Express.js, HTML, CSS, and JavaScript
• Deploy applications to Azure using Azure CLI commands
• Configure CORS policies to enable secure cross-origin API communication
• Test end-to-end application functionality including create, read, and update operations

Who is this lab for?

This lab is designed for:

• Cloud developers building full-stack applications on Azure
• Backend engineers learning serverless API development with Azure Functions
• Full-stack developers implementing 3-tier architectures in the cloud
• Students preparing for Azure certifications (AZ-204, AZ-104)
• DevOps engineers deploying and managing cloud-based web applications
• Solutions architects designing scalable multi-tier systems on Azure