A CloudKit developer designs, implements, and manages applications using Apple's CloudKit framework. This involves creating and organizing databases, managing user authentication and permissions, handling data storage and retrieval, and ensuring seamless data synchronization across multiple devices. They also troubleshoot issues, optimize performance, and maintain data privacy and security. Their work allows apps to leverage iCloud's cloud storage capabilities, facilitating the sharing of data between users and across various Apple devices. They must stay updated with advancements in the CloudKit technology to create efficient and innovative cloud-based applications.