Where are core data services (CDS) primarily developed in SAP S/4HANA?

Core Data Services (CDS) are primarily developed in the ABAP layer by IT users in SAP S/4HANA. This is because CDS is a specific technology that extends the capabilities of the ABAP programming model, enabling developers to define semantically rich data models directly in the ABAP environment.

By utilizing CDS, IT users can create complex views on the database that provide optimized access to data stored in the SAP HANA database, maintaining the necessary performance and efficiency expected in modern data processing. This modeling leads to simplified data consumption processes for applications running on SAP Fiori or other SAP interfaces, as they can directly leverage these optimized data structures created by ABAP developers.

Other layers mentioned, such as the SAP Fiori layer, focus on the presentation and user experience aspects of applications rather than the data modeling that CDS provides. While analytics key users may utilize CDS views for reporting and analytics, the primary development and technical configuration occur within the ABAP layer under the IT user role. Thus, the answer aligns with the context of how and where CDS is developed within the SAP S/4HANA architecture.