Jason Liu is a US ML engineer and the creator of Instructor (the most-used Python library for getting structured outputs from LLMs) and a long-running independent voice on the production-engineering side of LLM applications. He consults with companies on RAG implementations and is widely cited for the rigour of his approach to systematic RAG improvement.
His CourseFlix listing carries three Jason Liu courses: Systematically Improving RAG Applications, the accompanying Bonus Content module, and 3 Day AI Coding Accelerator. The RAG material is unusual for the depth it goes into the eval and feedback-loop side of production RAG systems — the parts of RAG work that separate a working RAG pipeline from one that hallucinates.
Material is paid and aimed at engineers running RAG in production who want to make the system measurably better rather than relying on prompt-engineering by intuition. For broader content, see CourseFlix's RAG category page.