Which type of flow is used for field updates in workflow rules?

The type of flow used for field updates in workflow rules is a Fast Field Update (Before-Save) Flow. This flow is designed to make immediate changes to record fields before the record is actually saved to the database. When a record that meets the criteria of a workflow rule is updated, this flow allows for the processing of those changes without waiting for additional processing that might occur after the record is saved. This results in more efficient updates, as the changes are applied in real time and do not require extra processing time, which is essential for maintaining data integrity and performance.

The other types of flows serve different purposes. A Record-Triggered Flow can perform actions after a record is saved, but it does not provide the same immediacy in field updates as a Fast Field Update. A Scheduled Path Flow is used to schedule actions to take place at a later time, rather than making immediate updates. Lastly, a Screen Flow is meant for user interaction and usually requires user input through a screen, making it unsuitable for automatic field updates that workflow rules entail.