Service layer on top of elasticsearch

We are on our ideation for developing a service layer on top of our elasticsearch nodes for multiple services that will query the nodes. We have come down to using either Nodejs or Python clients.

I dont think there is a clear winner like any dev choice. How should we go about choosing one when I/Os performance and caching opportunities are high on our list. Asking this questions to get clarity on several libraries available in both python and nodejs that would suit elasticsearch IO.

Test.
Test using data and queries that you expect to be processing on nodes with the same specs you are planning on using.