MyPersistentActor.scala

class MyPersistentActor extends PersistentActor {
  override def receiveCommand: Receive = {
    case c: Command ⇒ {
      validate(c).foreach { // 1. Validate
        events ⇒ persistAsync(events) { // 2. Persist
          e ⇒ 
           sender() ! respond(e) // 3. respond to sender
           downstream ! e // 4. Apply other side-effects
           bi ! AppEvent(currentState, e, context) // 5. Send event/state/context to BI
           ...
        }
      }
    }
    ...
  }
}