anchor.diff:  
   % print status when finished benchmark
   terminate(Reason, State) ->
  +    case erlang:get(worker_id) of
  +        1 -> finalize(Reason, State);
  +        _ -> void
  +    end.
  +
  +finalize(Reason, State) ->
       % debug output for prefix data
  -%%%    Fun = fun(K, _V, Acc) ->
  -%%%        [PrefixBin|_]= binary:split(K, <<$:>>),
  -%%%        case PrefixBin of
  -%%%            <<"1">> ->
  -%%%                [K|Acc];
  -%%%            _ ->
  -%%%                Acc
  -%%%        end
  -%%%    end,
  -%%%    List = leo_backend_db_api:fetch(State, <<"1:">>, Fun),
  -%%%    io:format(user, "[debug]prefix 1: list:~p~n", [List]),
  +    BackendDB    = basho_bench_config:get(backend_db,    'bitcask'),
  +    TargetPrefix = <<"123">>,
  +    Fun = case BackendDB of
  +        'bitcask' -> gen_prefix_fun(TargetPrefix);
  +        'leveldb' -> gen_prefix_fun(TargetPrefix)
  +    end,
  +    List = leo_backend_db_api:fetch(State, TargetPrefix, Fun),
  +    io:format(user, "[debug]prefix 123: list:~p~n", [List]),
       Ret = leo_backend_db_api:status(State),
       io:format(user, "[terminate]reason:~p status:~p~n", [Reason, Ret]),
       ok.
  
positive.code:     random:seed(),
      Ret = leo_backend_db_api:status(InstanceName),
      io:format(user, "[start]status:~p~n", [Ret]),
      {ok, InstanceName};
  new(_) ->
      InstanceName = basho_bench_config:get(instance_name, 'test_backend_db'),
  
negative.code: 
  run(prefix_get, _KeyGen, _ValueGen, State) ->
      TargetPrefix = gen_prefix(),
      BackendDB    = basho_bench_config:get(backend_db,    'bitcask'),
      Fun = case BackendDB of
          'bitcask' -> gen_prefix_fun(TargetPrefix);
          'leveldb' -> gen_prefix_fun(TargetPrefix)
      end,
      _List = leo_backend_db_api:fetch(State, TargetPrefix, Fun),
      {ok, State}.
  
  gen_prefix_fun(TargetPrefix) ->
      fun(K, _V, Acc) ->
          [PrefixBin|_]= binary:split(K, <<$:>>),
          case PrefixBin of
              TargetPrefix ->
  