- Optimize uses the new java high level rest client instead of the transport client
- The new rest-client is more flexible as it is not bound to a specific version in contrast to the transport client. Especially, if a client uses its own Elasticsearch this might become a problem.
- The performance is close to the transport client
- the new rest client does not ship with all the dependencies as the Transport client
- the transport client is going to become deprecated in Elasticsearch 6.x
Java high level rest client: https://www.elastic.co/guide/en/elasticsearch/client/java-rest/current/java-rest-high.html