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/ESSingleNodeTestCase.java
import java.nio.file.Path;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.TimeUnit;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import static org.elasticsearch.cluster.coordination.ClusterBootstrapService.INITIAL_MASTER_NODES_SETTING;
import static org.elasticsearch.discovery.SettingsBasedSeedHostsProvider.DISCOVERY_SEED_HOSTS_SETTING;
import static org.elasticsearch.test.NodeRoles.dataNode;
import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertAcked;
import static org.hamcrest.Matchers.equalTo;
import static org.hamcrest.Matchers.lessThanOrEqualTo;
/**
 * A test that keep a singleton node started for all tests that can be used to get
 * references to Guice injectors in unit tests.
 */
public abstract class ESSingleNodeTestCase extends ESTestCase {
    private static Node NODE = null;
    protected void startNode(long seed) throws Exception {
        assert NODE == null;
        NODE = RandomizedContext.current().runWithPrivateRandomness(seed, this::newNode);
        
        
        
        ClusterHealthResponse clusterHealthResponse = clusterAdmin().prepareHealth().setWaitForGreenStatus().get();
        assertFalse(clusterHealthResponse.isTimedOut());
        indicesAdmin().preparePutTemplate("one_shard_index_template")