code: func (updater *OCSPUpdater) oldOCSPResponsesTick(ctx context.Context, batchSize int) error {
  	tickStart := updater.clk.Now()
  	statuses, err := updater.findStaleOCSPResponses(tickStart.Add(-updater.ocspMinTimeToExpiry), batchSize)
  	if err != nil {
  		updater.stats.Inc("Errors.FindStaleResponses", 1)
  		updater.log.AuditErrf("Failed to find stale OCSP responses: %s", err)
  		return err
  	}
  	if len(statuses) == batchSize {
  		updater.stats.Inc("oldOCSPResponsesTick.FullTick", 1)
  	}
  	tickEnd := updater.clk.Now()
  	updater.stats.TimingDuration("oldOCSPResponsesTick.QueryTime", tickEnd.Sub(tickStart))
  
  	for _, s := range statuses {
  		if !s.IsExpired && tickStart.After(s.NotAfter) {
  			err := updater.markExpired(s)
  			if err != nil {
  				return err
  			}
  		}
  	}
  
  	return updater.generateOCSPResponses(ctx, statuses, updater.stats.NewScope("oldOCSPResponsesTick"))
  }
docs: // oldOCSPResponsesTick looks for certificates with stale OCSP responses and
  // generates/stores new ones