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
/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the Elastic License
 * 2.0 and the Server Side Public License, v 1; you may not use this file except
 * in compliance with, at your election, the Elastic License 2.0 or the Server
 * Side Public License, v 1.
 */
package org.elasticsearch.test;
import io.netty.util.ThreadDeathWatcher;
import io.netty.util.concurrent.GlobalEventExecutor;
import com.carrotsearch.randomizedtesting.RandomizedContext;
import com.carrotsearch.randomizedtesting.annotations.TestGroup;
import com.carrotsearch.randomizedtesting.generators.RandomNumbers;
import com.carrotsearch.randomizedtesting.generators.RandomPicks;
import org.apache.http.HttpHost;
import org.apache.lucene.search.Sort;
import org.apache.lucene.search.TotalHits;
import org.apache.lucene.tests.util.LuceneTestCase;
import org.elasticsearch.ExceptionsHelper;
import org.elasticsearch.action.ActionListener;