Amazon Elasticsearch Service now supports three Availability Zone deployments
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.
If you have already launched domains with “Zone Awareness” turned on (two AZ configuration), you can now easily reconfigure them to leverage three AZs. You can enable three AZ deployments for both existing and new domains at no extra cost using the AWS console, CLI or SDKs. Three AZs are supported in the following regions: US East (N. Virginia, Ohio), US West (Oregon), EU (Ireland, Frankfurt, London, Paris), Asia Pacific (Sydney, Tokyo, Singapore), and AWS China (Ningxia) region, operated by NWCD.
To learn more, read our documentation.