@Override
    public <T> boolean scheduleIfNotExists(SchedulableInstance<T> schedulableInstance) {
      return scheduleIfNotExists(
          schedulableInstance.getTaskInstance(),
          schedulableInstance.getNextExecutionTime(clock.now()));
    }
Will cause getScheduledExecutions(..) to return executions in priority order.
db-scheduler/src/main/java/com/github/kagkarlsson/scheduler/SchedulerClient.java