Since the site doesn't describe this in any detail: can you define 'necessity'? In other words, can you tell us anything about how and when your service decides to scale up or down, for dynos and for workers? And what have you done to avoid porpoising (to borrow an aviation term for lack of a better option coming to mind at the moment.)

Also, can your service scale workers all the way down to zero and then spark up the first worker upon the next job submission? Or can it only scale workers as low as one?