Is the idea that `self.config.process_interval` is supposed to match the interval at which this cron app is running. 

Considering that this app is not backfill based, what could happen is that it fails 3 times in a row (for some reason; e.g. unable to connect to rabbit) and eventually works on the fourth attempt, that means that this `start_time` will only be for the last 5 minutes. Not for the other 15 minutes under which it did not work.