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
public void tearDown() throws Exception {
        logger.trace("[{}#{}]: cleaning up after test", getTestClass().getSimpleName(), getTestName());
        ensureNoInitializingShards();
        SearchService searchService = getInstanceFromNode(SearchService.class);
        assertThat(searchService.getActiveContexts(), equalTo(0));
        assertThat(searchService.getOpenScrollContexts(), equalTo(0));
        super.tearDown();
        var deleteDataStreamsRequest = new DeleteDataStreamAction.Request("*");
        deleteDataStreamsRequest.indicesOptions(IndicesOptions.LENIENT_EXPAND_OPEN_CLOSED_HIDDEN);
        try {
            assertAcked(client().execute(DeleteDataStreamAction.INSTANCE, deleteDataStreamsRequest));
        } catch (IllegalStateException e) {
            
            
            if (e.getMessage().startsWith("failed to find action") == false) {
                throw e;
            }
        }
        var deleteComposableIndexTemplateRequest = new DeleteComposableIndexTemplateAction.Request("*");
        assertAcked(client().execute(DeleteComposableIndexTemplateAction.INSTANCE, deleteComposableIndexTemplateRequest).actionGet());
        var deleteComponentTemplateRequest = new DeleteComponentTemplateAction.Request("*");
        assertAcked(client().execute(DeleteComponentTemplateAction.INSTANCE, deleteComponentTemplateRequest).actionGet());
        assertAcked(indicesAdmin().prepareDelete("*").setIndicesOptions(IndicesOptions.LENIENT_EXPAND_OPEN_CLOSED_HIDDEN).get());
        Metadata metadata = clusterAdmin().prepareState().get().getState().getMetadata();
        assertThat(
            "test leaves persistent cluster metadata behind: " + metadata.persistentSettings().keySet(),
            metadata.persistentSettings().size(),
            equalTo(0)
        );
        assertThat(