How to build a web app with multiple subdomains using Nginx

The guide provides a comprehensive walkthrough on building a web application that supports multiple subdomains, using a variety of tools and services such as DNS configuration, Nginx setup, and SSL certificate installation with Certbot. It begins by explaining the need for custom subdomains in popular SaaS products and then delves into the technical requirements, including acquiring a domain, setting up a server on a cloud provider like AWS EC2, and configuring DNS records through a service like Amazon Route 53. The document elaborates on setting up Nginx as a reverse proxy to manage traffic between subdomains and the root domain and describes the use of the MERN stack (MongoDB, Express.js, React, Node.js) to build a simple CRUD application. Detailed instructions are provided for configuring Nginx to handle HTTPS requests using SSL certificates, creating a MongoDB database to store user data, and implementing Node.js with Express.js to route traffic between the root and subdomains using virtual hosts. The tutorial concludes with steps to initialize the server and verify the application's functionality, ensuring users can create custom subdomains linked to their profiles, while also offering a look at error handling and page rendering using EJS templates.