Hassan is correct that a timer won’t fire before it gets committed and that the process engine only commits when the process instance reaches a wait state. However, asyncBefore won’t help here since it is before and not after start. That means, when the asyncBefore job is created, the service task is not active yet and therefore the timer job does not exist yet. Timer events on service tasks will only work if the service task itself is a wait state. That is the case if it is implemented as an external task or if it is implemented via the asynchronous service task pattern.
Cheers,
Thorben