An Alto.js developer is responsible for creating and managing web applications using the Alto.js framework. They utilize this lightweight, intuitive JavaScript framework to build dynamic, scalable web applications with a focus on simplicity and efficiency. Their tasks include creating server-side application logic, connecting applications with other web services, and supporting front-end developers by integrating their work with the Alto.js application. They may also be responsible for managing and optimizing application databases, ensuring high performance and responsiveness. Furthermore, they collaborate with other team members to define and integrate features, always adhering to best coding practices.