private double growthRateHeadroom(Instant now) {
        if ( ! nodeRepository.zone().environment().isProduction()) return 1;
        double growthRateHeadroom = 1 + maxQueryGrowthRate(now) * scalingDuration().toMinutes();
        // Cap headroom at 10% above the historical observed peak
        if (queryFractionOfMax(now) != 0)
            growthRateHeadroom = Math.min(growthRateHeadroom, 1 / queryFractionOfMax(now) + 0.1);

        return adjustByConfidence(growthRateHeadroom, now);
    }
Returns the headroom for growth during organic traffic growth as a multiple of current resources.
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/autoscale/ClusterModel.java