anchor.diff:              {PutResult, undefined, undefined}
       end.
   
  +%% If backpressure is needed, sleep some interval and return `true'.
  +%% Otherwise, return `false'.
  +-spec maybe_backpressure_sleep(non_neg_integer()) -> boolean().
   maybe_backpressure_sleep(Siblings) ->
       BackpressureThreshold = riak_cs_config:get_env(
                                 riak_cs, manifest_siblings_bp_threashold, 5),
       maybe_backpressure_sleep(Siblings, BackpressureThreshold).
   
  +-spec maybe_backpressure_sleep(non_neg_integer(), non_neg_integer() | infinity) -> boolean().
   maybe_backpressure_sleep(Siblings, BackpressureThreshold)
     when Siblings < BackpressureThreshold ->
  -    ok;
  +    false;
   maybe_backpressure_sleep(Siblings, _BackpressureThreshold) ->
       MaxSleep = riak_cs_config:get_env(riak_cs, manifest_siblings_bp_max_sleep, 30*1000),
       Coefficient = riak_cs_config:get_env(riak_cs, manifest_siblings_bp_coefficient, 200),
  
positive.code:         {ok, RiakObject, Manifests} ->
              case update(RcPid, Manifests, RiakObject, WrappedManifests, Bucket, Key) of
                  {ok, _, _} = Res ->
                      maybe_backpressure_sleep(riakc_obj:value_count(RiakObject)),
                      Res;
                  OtherRes ->
                      OtherRes
              end;
  
negative.code:     SleepMS = crypto:rand_uniform(MeanSleepMS - Delta, MeanSleepMS + Delta),
      lager:debug("maybe_backpressure_sleep: Siblings=~p, SleepMS=~p~n", [Siblings, SleepMS]),
      ok = riak_cs_stats:update(manifest_siblings_bp_sleep, SleepMS * 1000),
      ok = timer:sleep(SleepMS),
      true.
  
  update(RcPid, OldManifests, OldRiakObject, WrappedManifests, Bucket, Key) ->
      NewManiAdded = riak_cs_manifest_resolution:resolve([WrappedManifests, OldManifests]),
  