Nest.js is being used to build an efficient Node.js application, paired with MySQL for the database. This tutorial guides users on how to connect a Nest.js RESTful API to a PlanetScale MySQL database, enabling them to perform CRUD operations such as creating, retrieving, editing, and deleting users. The connection process involves setting up a free Planetscale account, cloning an existing Nest.js project, installing dependencies, and defining the database parameters in a `.env` file. Users can test their API using Postman and experience the safety measures provided by PlanetScale, such as branching workflow and deploy requests, to protect against data loss and ensure database availability.