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.index.codec.CodecService;
import org.elasticsearch.index.engine.Segment;
import org.elasticsearch.index.mapper.MockFieldFilterPlugin;
import org.elasticsearch.index.translog.Translog;
import org.elasticsearch.indices.IndicesQueryCache;
import org.elasticsearch.indices.IndicesRequestCache;
import org.elasticsearch.indices.store.IndicesStore;
import org.elasticsearch.node.NodeMocksPlugin;
import org.elasticsearch.persistent.PersistentTasksCustomMetadata;
import org.elasticsearch.plugins.NetworkPlugin;
import org.elasticsearch.plugins.Plugin;
import org.elasticsearch.rest.RestStatus;
import org.elasticsearch.rest.action.RestCancellableNodeClient;
import org.elasticsearch.script.MockScriptService;
import org.elasticsearch.search.ConcurrentSearchTestPlugin;
import org.elasticsearch.search.MockSearchService;
import org.elasticsearch.search.SearchHit;
import org.elasticsearch.search.SearchService;
import org.elasticsearch.test.client.RandomizingClient;
import org.elasticsearch.test.disruption.NetworkDisruption;
import org.elasticsearch.test.disruption.ServiceDisruptionScheme;
import org.elasticsearch.test.store.MockFSIndexStore;
import org.elasticsearch.test.transport.MockTransportService;
import org.elasticsearch.transport.TransportInterceptor;
import org.elasticsearch.transport.TransportRequest;
import org.elasticsearch.transport.TransportRequestHandler;
import org.elasticsearch.transport.TransportService;
import org.elasticsearch.xcontent.NamedXContentRegistry;
import org.elasticsearch.xcontent.ToXContent;
import org.elasticsearch.xcontent.XContentBuilder;