TitanGraph slows down on commit()

Question

I am creating Titan-Graph through Java. Dynamo-db local is as a back-end. My problem is , on graph.tx().commit() it takes more time when i am creating 400+ vertices in graph. Time taken by commit() is about 10-15 minutes. My titan configurations are as follows :

BaseConfiguration conf = new BaseConfiguration();

    conf.setProperty("storage.backend", "com.amazon.titan.diskstorage.dynamodb.DynamoDBStoreManager");
    conf.setProperty("storage.dynamodb.client.endpoint", "http://localhost:4567");
    conf.setProperty("storage.batch-loading ", "true");
    conf.setProperty("storage.buffer-size", "10000");
    conf.setProperty("cache.db-cache", "true");
    conf.setProperty("index.search.backend", "elasticsearch");
    conf.setProperty("index.search.directory", "/tmp/searchindex");
    conf.setProperty("index.search.elasticsearch.client-only", "false");
    conf.setProperty("index.search.elasticsearch.local-mode", "true");

    TitanGraph graph = TitanFactory.open(conf);

please suggest me the solution for improving titan performance.