A Core Data developer is responsible for managing the model layer objects in an application. They design, build and manage the data models and databases, using Core Data, a persistent framework provided by Apple for iOS applications. Their tasks include defining entity descriptions, creating fetch requests to retrieve data, and managing context to track changes. They handle data storage, retrieval, filtering, and manipulation, ensuring efficient performance and data integrity. They also integrate the application’s data model with the user interface and resolve any data-related issues. Their role is critical in maintaining the smooth functionality of applications.