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 org.elasticsearch.cluster.metadata.Metadata;
import org.elasticsearch.cluster.routing.allocation.DiskThresholdSettings;
import org.elasticsearch.common.Priority;
import org.elasticsearch.common.Strings;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.common.util.concurrent.EsExecutors;
import org.elasticsearch.core.IOUtils;
import org.elasticsearch.core.TimeValue;
import org.elasticsearch.env.Environment;
import org.elasticsearch.env.NodeEnvironment;
import org.elasticsearch.index.Index;
import org.elasticsearch.index.IndexService;
import org.elasticsearch.index.IndexSettings;
import org.elasticsearch.indices.IndicesService;
import org.elasticsearch.indices.breaker.HierarchyCircuitBreakerService;
import org.elasticsearch.node.MockNode;
import org.elasticsearch.node.Node;
import org.elasticsearch.node.NodeValidationException;
import org.elasticsearch.plugins.Plugin;
import org.elasticsearch.script.MockScriptService;
import org.elasticsearch.search.ConcurrentSearchTestPlugin;
import org.elasticsearch.search.SearchService;
import org.elasticsearch.search.internal.SearchContext;
import org.elasticsearch.test.rest.ESRestTestCase;
import org.elasticsearch.transport.TransportSettings;
import org.elasticsearch.xcontent.NamedXContentRegistry;
import org.elasticsearch.xcontent.XContentBuilder;
import org.junit.AfterClass;
import org.junit.BeforeClass;
import java.io.IOException;