Amazon Elasticsearch Service now supports open source Elasticsearch 6.5 and Kibana 6.5. The new version of Elasticsearch and Kibana offers several new features and improvements, including auto-interval date histogram, conditional token filters, and early termination support for min/max aggregations. 

You can now create new domains running Elasticsearch 6.5 and also easily upgrade existing 5.6 and 6.x domains with no downtime using in-place version upgrades.