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
.setPatterns(Collections.singletonList("*"))
            .setOrder(0)
            .setSettings(Settings.builder().put(IndexMetadata.SETTING_NUMBER_OF_SHARDS, 1).put(IndexMetadata.SETTING_NUMBER_OF_REPLICAS, 0))
            .get();
        indicesAdmin().preparePutTemplate("random-soft-deletes-template")
            .setPatterns(Collections.singletonList("*"))
            .setOrder(0)
            .setSettings(Settings.builder().put(IndexSettings.INDEX_SOFT_DELETES_RETENTION_OPERATIONS_SETTING.getKey(), between(0, 1000)))
            .get();
    }
    private static void stopNode() throws IOException, InterruptedException {
        Node node = NODE;
        NODE = null;
        IOUtils.close(node);
        if (node != null && node.awaitClose(10, TimeUnit.SECONDS) == false) {
            throw new AssertionError("Node couldn't close within 10 seconds.");
        }
    }
    @Override
    public void setUp() throws Exception {
        super.setUp();
        
        long seed = random().nextLong();
        
        
        if (NODE == null) {
            startNode(seed);
        }
    }
    @Override