changeKey.java

public static String transformKey(String key, Row record) {
    /**
     * TODO: Change the existing key here, by a new key
     *
     * <p>Here we just reverse the key, as a demo. Ideally, you should test different strategies,
     * test the performance obtained with each key transform strategy, and then decide how you need
     * to change the keys.
     */
    return StringUtils.reverse(key);
  }