Well, the `AppLockedException` is just a notification, that another operation is already in progress. We can't tell how long this operation will take, could be 10ms, could be 30min (in case of an upgrade). We don't want the app definition to change or the app to scale during an upgrade and we don't want to block for 30 mins. So the user has to decide what he will do. Basically he has to try again later.