docs: public Map<String, VectorClock> getReplicatedVectorClock(String serviceName, String memberUUID) {
          final ReplicatedVectorClockId id = new ReplicatedVectorClockId(serviceName, memberUUID);
          final Map<String, VectorClock> clocks = replicatedVectorClocks.get(id);
          return clocks != null ? clocks : Collections.<String, VectorClock>emptyMap();
      }