What magic is supposed to handle processing at the time an auction ends?
It's your app. You bring the magic. This could be something stupid-simple, like every 5 seconds a Cron job hits `rails runner -e production 'Auction.handle_finished'`.
No matter what it is, you will have written it. There's nothing magical that happens in Rails that knows when a particular time has passed unless you wake it up and ask it (and write something to handle that case).