- Optimize works with Elasticsearch 6.3, 6.4, 6.5
- There are Jenkins jobs running every night that tests the Elasticsearch support
- The supported Elasticsearch versions are added to the supported evnironment in the Technical guide. Also there is a warning that says: "Other Elasticsearch versions might work as well, but those are not officially supported and therefore it is strongly recommended to use one of the stated versions."
- the supported Elasticsearch versions can be read on the download page