/** The key of the configuration. e.g. 5 */
    String INDEX_number_of_shards = "index.number_of_shards";

    /** The key of the configuration. e.g. 0-1 */
    String INDEX_auto_expand_replicas = "index.auto_expand_replicas";

    /** The key of the configuration. e.g. SHA-512 */
    String INDEX_ID_DIGEST_ALGORITHM = "index.id.digest.algorithm";

    /** The key of the configuration. e.g. admin */