Amazon Elasticsearch Service now enables you to deploy your instances across three Availability Zones (AZs) providing better availability for your domains. If you enable replicas for your Elasticsearch indices, Amazon Elasticsearch Service distributes the primary and replica shards across nodes in different AZs to maximize availability. If you have configured dedicated master nodes while using multi-AZ deployment, they are automatically placed into three AZs to ensure that your cluster can elect a new master even in the rare event of an AZ disruption.