Which technology is a prerequisite for populating the cloud-based directory in a federated identity solution?

A notification tool handles alerts and messaging but has no capability to replicate or populate identity objects into a cloud directory.

A message queuing tool manages asynchronous communication between services but is not responsible for synchronizing or provisioning identity data to a cloud directory.

A security token tool (e.g., an STS/ADFS) issues authentication tokens after identities already exist in the directory, but it cannot populate or replicate the directory itself.

A synchronization tool (such as Microsoft Entra Connect/Azure AD Connect) is a prerequisite because it replicates user identity objects and attributes from the on-premises directory (e.g., Active Directory) to the cloud-based directory (e.g., Microsoft Entra ID). Without this synchronization, the cloud directory would have no user accounts to authenticate against, making federated sign-in impossible. The sync process ensures that identity data is consistent and available in the cloud before federation tokens are issued.