code: func (f *fanout) StartTime() (int64, error) {
  	// StartTime of a fanout should be the earliest StartTime of all its storages,
  	// both primary and secondaries.
  	firstTime, err := f.primary.StartTime()
  	if err != nil {
  		return int64(model.Latest), err
  	}
  
  	for _, storage := range f.secondaries {
  		t, err := storage.StartTime()
  		if err != nil {
  			return int64(model.Latest), err
  		}
  		if t < firstTime {
  			firstTime = t
  		}
  	}
  	return firstTime, nil
  }
docs: // StartTime implements the Storage interface.