Exam Certified Platform App Builder topic 1 question 22 discussion

External ID does not have to be unique. Though you can make it unique with additional checkbox.

An external ID CAN be marked as case sensitive.

Answer is A & D. An external Id may not be marked a Unique

For External ID, they can be unique just for a certain group of records. For the whole records in a object, they can be duplicate.

I would say A and B. External IDs are not unique ID. External IDs are used for data migration, and I dont recall it is case sensitive https://help.salesforce.com/s/articleView?id=000325076&type=1 https://help.salesforce.com/s/articleView?id=sf.faq_import_general_what_is_an_external.htm&type=5

A and D: External ID in Salesforce is a custom field that has the “External ID” attribute checked meaning that it contains unique record identifiers from a system outside of Salesforce. When we select this option the import wizard will detect existing records in Salesforce that have the same External Identification. This operation is case-insensitive but if the custom field has a separate “Unique” attribute then the case sensitive option for that field is selected which means Uppercase and Lowercase letters will not be considered identical. https://shreysharma.com/external-id-record-id-security-token/