Updating users via the API is slow compared to most other object types. For example, updating a user's home group takes about 2 seconds. Performing this via the bulk update API doesn't improve this. I suspect WF is performing unnecessary actions when making simple updates to the user objects.
This is affecting our ability to bulk update the Home Group for 380k users via the API. What should normally take a couple hours is taking over a week.
I recommend that the engineering team update the code so that it only does the extra processing when certain fields change on a user. WF already does this for tasks. For example, if a task is renamed, it doesn’t trigger the timeline engine to execute…it just updates the database. But if the task’s duration changes, the timeline engine kicks into gear.