Regarding the compatibility shim approach I think this should be avoided if at all possible. I don't think using Jest gets away from needing version-specific ES client code to support other (node/transport) clients in code base (unless we drop node/transport clients in favor of HTTP-only) and definitely to supported running embedded ES in testing/release. Unless I'm wrong about this then if we did want to do compatibility shim approach I think we'd end up needing to create separate JanusGraph releases tied to the specific version of ES. This is not currently necessary as one JanusGraph release can service all versions for relevant modules (e.g. hbase), though I don't know if this will come up again with cassandra-cql work. I really don't think this complexity should be introduced just to continue supporting ES 1.x.