private OptionalDouble averageQueryRate(Instant now) {
        if (averageQueryRate.isPresent()) return averageQueryRate;
        return averageQueryRate = clusterTimeseries().queryRate(scalingDuration(), now);
    }
Returns the average query rate in the scaling window.
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/autoscale/ClusterModel.java