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
"test leaves transient cluster metadata behind: " + metadata.transientSettings().keySet(),
            metadata.transientSettings().size(),
            equalTo(0)
        );
        GetIndexResponse indices = indicesAdmin().prepareGetIndex()
            .setIndicesOptions(IndicesOptions.LENIENT_EXPAND_OPEN_CLOSED_HIDDEN)
            .addIndices("*")
            .get();
        assertThat(
            "test leaves indices that were not deleted: " + Strings.arrayToCommaDelimitedString(indices.indices()),
            indices.indices(),
            equalTo(Strings.EMPTY_ARRAY)
        );
        if (resetNodeAfterTest()) {
            assert NODE != null;
            stopNode();
            
            startNode(random().nextLong());
        }
    }
    @BeforeClass
    public static void setUpClass() throws Exception {
        stopNode();
    }
    @AfterClass
    public static void tearDownClass() throws Exception {
        stopNode();
        ESIntegTestCase.awaitGlobalNettyThreadsFinish();
    }
    /**