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
server/src/main/java/org/elasticsearch/search/SearchService.java
}
    private void setEnableSearchWorkerThreads(boolean enableSearchWorkerThreads) {
        this.enableSearchWorkerThreads = enableSearchWorkerThreads;
    }
    private void setEnableQueryPhaseParallelCollection(boolean enableQueryPhaseParallelCollection) {
        this.enableQueryPhaseParallelCollection = enableQueryPhaseParallelCollection;
    }
    private static void validateKeepAlives(TimeValue defaultKeepAlive, TimeValue maxKeepAlive) {
        if (defaultKeepAlive.millis() > maxKeepAlive.millis()) {
            throw new IllegalArgumentException(
                "Default keep alive setting for request ["
                    + DEFAULT_KEEPALIVE_SETTING.getKey()
                    + "]"
                    + " should be smaller than max keep alive ["
                    + MAX_KEEPALIVE_SETTING.getKey()
                    + "], "
                    + "was ("
                    + defaultKeepAlive
                    + " > "
                    + maxKeepAlive
                    + ")"
            );
        }
    }
    private void setKeepAlives(TimeValue defaultKeepAlive, TimeValue maxKeepAlive) {
        validateKeepAlives(defaultKeepAlive, maxKeepAlive);
        this.defaultKeepAlive = defaultKeepAlive.millis();
        this.maxKeepAlive = maxKeepAlive.millis();
    }
    private void setDefaultSearchTimeout(TimeValue defaultSearchTimeout) {