A Google or Instagram API developer designs, implements, and manages APIs (Application Programming Interfaces) that allow third-party services to interact with Google or Instagram platforms. They are responsible for ensuring the API's functionality, reliability, and security. They develop features that allow data exchange between systems, like pulling user data or posting content. They also document the API for other developers, handle updates, and troubleshoot issues. Developers constantly collaborate with other teams to understand their needs and ensure that the API meets these requirements. Their role is crucial in enabling seamless integration and enhancing user experience.