Explanation
Using Change Data Capture (CDC) to update downstream systems accordingly when a record changes is a solution that can handle this requirement by capturing data changes in Salesforce and sending them to external systems via a publish-subscribe model. This way, the external systems can receive near real-time updates from Salesforce and synchronize their data accordingly. Designing an MDM solution that maps external ID's to the Salesforce record ID is a solution that can handle this requirement by creating a master data hub that stores and manages the unique identifiers of each system and their relationships. This way, the MDM solution can ensure data quality, consistency, and accuracy across systems. Locally caching external ID's at the middleware layer and designing business logic to map updates between systems is not a good solution because it can introduce performance and scalability issues, as well as increase the complexity and maintenance cost of the middleware layer. Storing unique identifiers in an External ID field in Salesforce and using this to update the proper records across systems is not enough to handle this requirement, as it does not address how to update Salesforce with record changes from external systems. Reference: Salesforce Integration Architecture Designer Resource Guide, page 27-28