aggregation

            // The LatencyStat object is a POJO with three fields: bucket, percentile and latency
            // The goal is to get a new List<LatencyStat> with one object per (bucket, percentile) combination
            // averaging the latency value between them.
            Map<String, Map<Double, List<SearchLatencyProbe.LatencyStat>>> foo = nodes.stream()
                    .flatMap(n -> n.statDetails.latencies.stream())
                    .collect(Collectors.groupingBy(LatencyStat::getBucket,
                            Collectors.groupingBy(LatencyStat::getPercentile)));
            List<LatencyStat> allNodes = new ArrayList<>();
            for (Map.Entry<String, Map<Double, List<LatencyStat>>> bucketEntry : foo.entrySet()) {
                for (Map.Entry<Double, List<LatencyStat>> percentileEntry : bucketEntry.getValue().entrySet()) {
                    double latency = percentileEntry.getValue().stream().mapToDouble(LatencyStat::getLatencyMs).average().orElse(0D);
                    allNodes.add(new LatencyStat(bucketEntry.getKey(), percentileEntry.getKey(), latency));
                }
            }