A Google API developer builds, tests, and maintains integrations for Google's Application Programming Interfaces (APIs). These APIs enable interaction with Google services and data. The developer uses programming languages like Python, JavaScript, or Java to create software that can retrieve, manipulate, and store data from Google's services. They are responsible for understanding the functionality of different APIs, such as Google Maps, Google Calendar, or Google Analytics, and implementing them into applications or websites. They also ensure the security of data transactions, handle API limitations, and troubleshoot any issues that arise during the development process.