Marketing Cloud should be the system of record for lifetime engagement tracking and history, as well as other data for personalization or segmentation, as it is the system that collects and analyzes the customer's interactions and behaviors across multiple channels and touchpoints. Marketing Cloud can also use features like Audience Builder and Contact Builder to create unified customer profiles and segments based on various data sources3 . Service Cloud should be the system of record for storing primary attributes (name, address, birthday, phone, and email) about the customer, as it is the system that represents a person across multiple Salesforce clouds and can store and manage the customer's consent and compliance preferences using features like Individual object, Data Protection and Privacy, and Consent Management .