The consultant should review the Relationships object first when noticing that there are more than 10,000 child records associated to a single parent record for the institution that is experiencing record locking and sharing performance issues in a Salesforce org with EDA. The Relationships object is an object in EDA that allows users to store information about how two Contacts are related to each other, such as parent-child, sibling, or spouse. The Relationships object can cause record locking and sharing performance issues in a Salesforce org with EDA if there are too many child records associated to a single parent record, such as a Contact with many Relationships or Affiliations. The consultant should review the Relationships object first when noticing that there are more than 10,000 child records associated to a single parent record for the institution that is experiencing record locking and sharing performance issues in a Salesforce org with EDA by checking if there are any data skew or ownership skew issues and applying best practices to resolve them. Accounts or Affiliations are not objects that the consultant should review first when noticing that there are more than 10,000 child records associated to a single parent record for the institution that is experiencing record locking and sharing performance issues in a Salesforce org with EDA. Reference:
https://powerofus.force.com/s/article/EDA-Relationships
https://developer.salesforce.com/docs/atlas.en-us.salesforce_large_data_volumes_bp.meta/salesforce_large_data_volumes_bp/ldv_deployments_introduction.htm