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 Collections.emptySet();
    }
    protected void beforeIndexDeletion() throws Exception {
        cluster().beforeIndexDeletion();
    }
    public static TestCluster cluster() {
        return currentCluster;
    }
    public static boolean isInternalCluster() {
        return (currentCluster instanceof InternalTestCluster);
    }
    public static InternalTestCluster internalCluster() {
        if (isInternalCluster() == false) {
            throw new UnsupportedOperationException("current test cluster is immutable");
        }
        return (InternalTestCluster) currentCluster;
    }
    public ClusterService clusterService() {
        return internalCluster().clusterService();
    }
    public static Client client() {
        return client(null);
    }
    public static Client client(@Nullable String node) {
        if (node != null) {
            return internalCluster().client(node);
        }
        Client client = cluster().client();
        if (frequently()) {
            client = new RandomizingClient(client, random());