Amazon Elasticsearch Service (ES) is a managed service to host Elasticsearch instances.

To harden domain (cluster) data in case of unauthorized access, ES provides
data-at-rest encryption if the Elasticsearch version is 5.1 or above. Enabling
encryption at rest will help protect:

* indices
* logs
* swap files
* data in the application directory
* automated snapshots

Thus, if adversaries gain physical access to the storage medium, they cannot access the data.