auction site, processing at auctions end time

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).