A Lean Startup Minimum Viable Product (MVP) developer is responsible for building the most basic version of a product that delivers the core value proposition. Their goal is to create an MVP with just enough features to satisfy early customers and provide feedback for future product development. They follow the principles of the Lean Startup methodology, focusing on learning about customer needs and testing assumptions as quickly and efficiently as possible. This involves rapid prototyping, continuous testing, and iterating based on user feedback and data. Ultimately, their work helps to minimize waste, reduce risks, and increase the chances of business success.