I was wondering if it would be a good idea to use callLater in Twisted to keep track of auction endings. It would be a callLater on the order of 100,000's of seconds, though does that matter? Seems like it would be very convenient. But then again it seems like a horrible idea if the server crashes.
Keeping a database of when all the auctions are ending seems like the most secure solution, but checking the whole database each second to see if any auction has ended seems very expensive.
If the server crashes, maybe the server can recreate all the callLater's from database entries of auction end times. Are there other potential concerns for such a model?
One of the Divmod projects, Axiom, might be applicable here. Axiom is an object database. One of its unexpected, useful features is a persistent scheduling system.
You schedule events using APIs provided by the database. When the events come due, a callback you specified is called. The events persist across process restarts, since they're represented as database objects. Large numbers of scheduled events are supported, by only doing work to keep track when the next event is going to happen.
The canonical Divmod site went down some time ago (sadly the company is no longer an operating concern), but the code is all available at http://launchpad.net/divmod.org and the documentation is being slowly rehosted at http://divmod.readthedocs.org/.