It looks like Elasticsearch is currently missing support for concurrent searching and that this is a major prospective optimization to reduce latency.

Digression: this is not the topic at hand but I personally consider the fork OpenSearch to be an historical tragedy of duplication of work and a segregation of improvements. What would be even more anti-utilitarist would be to blindly *ignore* each other advances towards making better search.

Lucene concurrent search APIs are probably among the most important feature/optimization currently not leveraged by Elasticsearch.
The fork OpenSearch has a [pull request](https://github.com/opensearch-project/OpenSearch/pull/1500) implementing support for it.

See also the [corresponding issue](https://github.com/opensearch-project/OpenSearch/issues/1286) 

I believe it would be great for end users if you could take inspiration from the PR and work on this feature.

Great blog about the Lucene feature:
https://blog.mikemccandless.com/2019/10/concurrent-query-execution-in-apache.html?m=1
See also those performance results:
https://engineeringblog.yelp.com/2021/09/nrtsearch-yelps-fast-scalable-and-cost-effective-search-engine.html
test/framework/src/main/java/org/elasticsearch/test/ESIntegTestCase.java
return restClient;
    }
    protected static RestClient createRestClient() {
        return createRestClient(null, "http");
    }
    protected static RestClient createRestClient(RestClientBuilder.HttpClientConfigCallback httpClientConfigCallback, String protocol) {
        NodesInfoResponse nodesInfoResponse = clusterAdmin().prepareNodesInfo().get();
        assertFalse(nodesInfoResponse.hasFailures());
        return createRestClient(nodesInfoResponse.getNodes(), httpClientConfigCallback, protocol);
    }
    protected static RestClient createRestClient(
        final List<NodeInfo> nodes,
        RestClientBuilder.HttpClientConfigCallback httpClientConfigCallback,
        String protocol
    ) {
        List<HttpHost> hosts = new ArrayList<>();
        for (NodeInfo node : nodes) {
            if (node.getInfo(HttpInfo.class) != null) {
                TransportAddress publishAddress = node.getInfo(HttpInfo.class).address().publishAddress();
                InetSocketAddress address = publishAddress.address();
                hosts.add(new HttpHost(NetworkAddress.format(address.getAddress()), address.getPort(), protocol));
            }
        }
        RestClientBuilder builder = RestClient.builder(hosts.toArray(new HttpHost[hosts.size()]));
        if (httpClientConfigCallback != null) {
            builder.setHttpClientConfigCallback(httpClientConfigCallback);
        }
        return builder.build();
    }
    /**