Reminds me of "Project Thor" from my university days. Course registrations were online, but in phases, e.g. Seniors for a week, then Juniors for a week, and so down the line.

However, many students would snag a spot in a course only to drop it as they shuffled courses around. There existed a "queue" for the overflow, but it appeared to work as a CRON job or otherwise involved a human in the loop as one would routinely see:

Spanish 102 (Registered: (29/30), Queued:(60))

While in this state, one could simply click on the course and register, completely bypassing this poorly designed queue. So, naturally, I wrote a script to scrape the site on once a minute (hammering it, and so Project Thor) and alert me once a slot had opened up. Eventually provided this service to my friends as well.