code: static public Key make(byte[] kb, byte rf) {
      if( rf == -1 ) throw new IllegalArgumentException();
      Key key = new Key(kb);
      Key key2 = H2O.getk(key); // Get the interned version, if any
      if( key2 != null ) // There is one! Return it instead
        return key2;
  
      // Set the cache with desired replication factor, and a fake cloud index
      H2O cloud = H2O.CLOUD; // Read once
      key._cache = build_cache(cloud._idx-1,0,0,rf);
      key.cloud_info(cloud); // Now compute & cache the real data
      return key;
    }
docs: Make new Keys.  Optimistically attempt interning, but no guarantee.