Scheduler takes the frequency constant from the application.conf and uses the Actor system to send an update message (the content does not matter; SchedulerActor reacts to any message) to SchedulerActor every X seconds:

class Scheduler @Inject()
    (val system: ActorSystem, @Named("scheduler-actor") val schedulerActor: ActorRef, configuration:     Configuration)(implicit ec: ExecutionContext) {
    //constants.frequency is set in conf/application.conf file
    val frequency = configuration.getInt("constants.frequency").get
    var actor = system.scheduler.schedule(
    0.microseconds, //initial delay: whether execution starts immediately after app launch
    frequency.seconds, //every X seconds, specified above
    schedulerActor,
    "update")
}