Definition: It's a config file in Elasticsearch, used for defining cluster settings. In summary: - Defines the name of the index to use (es.cluster.index.name) - Specifies how many documents per page (es.cluster.query.num) - Specifies how long documents should be stored in cache (es.cluster.store.size) - Defines how frequently new documents are considered part of the update cycle (es.cluster.update.interval)