A single request can update maximum 500 users at once. If a request payload contains more than 500 aliases only first 500 aliases will be processed and only 500 users will be updated.
Updates of 501 users and above can be achieved by performing more than one API request.
API allows up to 100 requests per minute. When updating more than 50,000 users at a time calls to the API has to be spread in time to avoid breaching the limit. Calls are counted cumulatively for each user's IP address across all API endpoints.
Try It! to start a request and see the response here!