To create a chat application using NestJS with real-time messaging and notifications, you would typically follow these steps:

Setup NestJS Project: Initialize a new NestJS project as your backend framework. Integrate Socket.io: Use Socket.io with NestJS for real-time messaging. You'll need to set up a Gateway in NestJS that listens for and emits events. MySQL Database: Integrate MySQL for data storage. This involves setting up TypeORM or Sequelize with NestJS and creating models for your chat data. RabbitMQ for Notifications: Use RabbitMQ to handle real-time notifications. This would require setting up a RabbitMQ server and integrating it with NestJS using amqp library or NestJS's built-in microservices package. Each step involves specific configurations and code implementations:

For Socket.io, you'll configure events such as connection, message, and disconnect. For MySQL, you'll define entities and repositories to interact with the database. For RabbitMQ, you'll define message patterns and queues to publish and subscribe to notifications. Remember to handle authentication, validation, and error management across your application for security and robustness.