Final answer:
Core Data Services (CDS) are developed in the SAP HANA database layer by the Analytics key user.
Step-by-step explanation:
Core Data Services (CDS) are developed in the SAP HANA database layer by the Analytics key user. They are not developed in the ABAP layer of the SAP S/4HANA system or by the IT user. CDS is a data modeling infrastructure provided by SAP, allowing developers to define and consume semantically rich data models in the HANA database.