Batch User Processing

We get a lot of requests from our customer to do things for users in bulk.  This sometimes involves 100k+ users.  It might be adding users, adding users to roles, removing them, etc...  We have been trying to write things so that the requests can be accomplished without dev involvement after the initial request.  So, for instance, we might write a page that allows a user with the correct access to upload a CSV that will then be parsed and use that to add the users to a specified role.  This works to a point.  However, it takes a bit of time for each user.  If the list gets too big, the HTTP request times out.   What we would like to do in this case is import the CSV to a table and execute a stored procedure that would add those users to the specified role.  The user would receive a notification that the process completed with info on the success and number of users processed.   We might also want to take a list and ensure that a Sitefinity account is created for each user in the list (creating one for each user that is not).

I can find a lot of info on using the API for this, but nothing at all on how to do anything from the database side.  Is there any documentation available on how to do this kind of thing?

We could profile the database while doing this in code, but that does not always work out so well in my experience.