A company uses Salesforce to sell products to customers.

This requirement involves a complex, multi-step integration where an external system (PIM) drives data changes in Salesforce across multiple objects (Product2 and PricebookEntry) and requires a lookup to a specific configuration (Custom Setting). While the standard Salesforce REST API can create records, it would require the PIM to manage the sequencing and the lookup logic for the Pricebook.

A Custom Apex REST (Option B) service is the optimal solution because it allows the developer to expose a single endpoint to the PIM. The PIM can send a single JSON payload representing the product. The Apex code then takes over to:

Upsert the Product2 record based on an External ID.

Retrieve the Pricebook2 ID from the Custom Setting.

Query and upsert the corresponding PricebookEntry record.

This "wraps" the entire business process into a single transaction, ensuring data integrity (either both records are updated, or neither is) and reducing the number of round-trips the external system must make. Option A is for creating trees of records but doesn't easily support the logic of checking custom settings or existing records for upserting. Option C is for Flow/Process Builder, and Option D is for security auditing. Custom Apex REST provides the necessary flexibility for complex cross-object integration logic.

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