For cluster configuration, the API Gateway Data Store instances should also be clustered using Elasticsearch clustering properties, by modifying the SAG_root/InternalDataStore/config/elasticsearch.yml file on each instance. You must provide the cluster configurations in the elasticsearch.yml file in the SAG_root/InternalDataStore/config/ folder before starting the Elasticsearch for the very first time. When you start Elasticsearch, the node auto-bootstraps itself into a new cluster. You cannot change the configuration after bootstrap and thus, Elasticsearch does not merge separate clusters together after they have formed, even if you subsequently try and configure all the nodes into a single cluster. For more information, see the Elasticsearch documentation on clustering at https://www.elastic.co/.