A Bitly developer works with Bitly's platform, a URL shortening service and a link management platform. They are responsible for creating and optimizing software that enables users to shorten, brand, share, and analyze their links. Their tasks include developing the platform’s functionality, enhancing its performance, integrating it with other systems, and fixing bugs. They also work on ensuring the security of the platform, maintaining its databases, and providing technical support to its users. They utilize various programming languages and work closely with other developers, UI/UX designers, and data analysts to improve the overall user experience.