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
import org.elasticsearch.common.io.stream.NamedWriteableRegistry;
import org.elasticsearch.common.network.NetworkAddress;
import org.elasticsearch.common.network.NetworkModule;
import org.elasticsearch.common.regex.Regex;
import org.elasticsearch.common.settings.Setting;
import org.elasticsearch.common.settings.Setting.Property;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.common.transport.TransportAddress;
import org.elasticsearch.common.unit.ByteSizeUnit;
import org.elasticsearch.common.unit.ByteSizeValue;
import org.elasticsearch.common.util.Maps;
import org.elasticsearch.common.util.concurrent.EsRejectedExecutionException;
import org.elasticsearch.common.util.concurrent.ThreadContext;
import org.elasticsearch.common.xcontent.ChunkedToXContent;
import org.elasticsearch.common.xcontent.XContentHelper;
import org.elasticsearch.core.IOUtils;
import org.elasticsearch.core.Nullable;
import org.elasticsearch.core.TimeValue;
import org.elasticsearch.core.Tuple;
import org.elasticsearch.env.Environment;
import org.elasticsearch.env.TestEnvironment;
import org.elasticsearch.gateway.PersistedClusterStateService;
import org.elasticsearch.health.node.selection.HealthNode;
import org.elasticsearch.http.HttpInfo;
import org.elasticsearch.index.Index;
import org.elasticsearch.index.IndexModule;
import org.elasticsearch.index.IndexSettings;
import org.elasticsearch.index.MergePolicyConfig;
import org.elasticsearch.index.MergeSchedulerConfig;
import org.elasticsearch.index.MockEngineFactoryPlugin;