In this tutorial, Mervin Praison introduces NotDiamond, a model routing service designed to optimize AI application performance and reduce costs. He explains the concept of model routing, where simple queries are directed to weaker models while complex queries are handled by stronger models like GPT-4. Mervin provides a step-by-step guide on setting up NotDiamond, including how to integrate it into applications and create user interfaces using Chainlit. He demonstrates the practical implementation of model routing in a RAG (Retrieval-Augmented Generation) application, showcasing how to index documents and route queries based on complexity. The tutorial emphasizes the benefits of using NotDiamond to enhance efficiency and manage AI resources effectively, making it a valuable tool for AI developers looking to streamline their applications.