What must be present in the system before child records can be loaded in Bulk API?

For child records to be successfully loaded using the Bulk API in Salesforce, it is essential that the parent records are established in the system beforehand. This requirement arises from the relational nature of data in Salesforce, where child records rely on the existence of parent records to maintain their relationships.

When you load child records, they often reference a unique identifier from the parent records, typically known as an external ID or Salesforce ID. Without the parent records already being present, the child records cannot link correctly, which would lead to errors during the loading process or result in orphaned records that do not accurately reflect their associated parent entities.

This relationship ensures data integrity and enforces the dependencies that exist between parent and child records. Therefore, establishing the parent records first is a crucial step in the process of loading child records.