Which API client is most performant to access Elasticsearch?
All client libraries are HTTP based apart from the Java Transport client, which is being deprecated. I am not sure the client has a huge impact on performance as most of the request processing time is likely to be used within Elasticsearch.
I use python, but rewrote a pretty simple api task in Powershell for another team's use. Powershell was much slower. I added timers to measure the call time vs. the code time, it was the code. This was a scroll api call, so there were many calls retrieving a block of events at a time, powershell seemed slow iterating over the returned items.
Most of the available client libraries use connection pools with persistent connections which removed the need to constantly recreate connections. As far as I know there is no client library for powershell which will make it slower.