What is Cross-Cluster Replication (CCR) and Cross-Cluster Search (CCS)?

Cross-Cluster Replication (CCR) continuously replicates indices from a leader cluster to one or more follower clusters. It enables disaster recovery (automatic failover to a replica cluster in another data center), geo-proximity (replicate data to a local cluster to reduce search latency for users in different regions), and centralized reporting (aggregate data from multiple regional clusters into a single reporting cluster). Cross-Cluster Search (CCS) allows a single search query to transparently execute across multiple clusters and return merged results. With CCS, you can search cluster1:logs-*,cluster2:logs-* in one query. CCS is useful for federated search across multiple independent Elasticsearch clusters without physically consolidating data.