private static ClusterState derivedStateOf(ClusterStateBundle state, String space) {
        return state.getDerivedBucketSpaceStates().getOrDefault(space, AnnotatedClusterState.emptyState()).getClusterState();
    }
Represents the absolute cluster states (baseline + derived) for a given version
as well as the relative diffs (baseline + derived) since the previous version.
clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/ClusterStateHistoryEntry.java