private double maxQueryGrowthRate(Instant now) {
        if (maxQueryGrowthRate != null) return maxQueryGrowthRate;
        return maxQueryGrowthRate = clusterTimeseries().maxQueryGrowthRate(scalingDuration(), now);
    }
Returns the predicted max query growth rate per minute as a fraction of the average traffic
in the scaling window.
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/autoscale/ClusterModel.java