The scenario if it helps: I'm building a reminder kind of service that anybody can use to remind them to do something and there could end up being tens of thousands of reminders at any time. The reminders might be for one message 20 minutes from now, might be every 5 minutes, might be every day at 8:03 AM, might be every last Friday of every second month at midnight. Accuracy isn't too important so if something is off by some number of seconds or minutes that's okay. But outages, restarts, etc. must not cause a reminder to be missed. Basically some kind of reliable cron daemon for actors.