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
if (type != null) {
            createIndexRequestBuilder.setMapping(mappings);
        }
        return createIndex(index, createIndexRequestBuilder);
    }
    protected IndexService createIndex(String index, CreateIndexRequestBuilder createIndexRequestBuilder) {
        assertAcked(createIndexRequestBuilder.get());
        
        
        ClusterHealthResponse health = clusterAdmin().health(
            new ClusterHealthRequest(index).waitForYellowStatus().waitForEvents(Priority.LANGUID).waitForNoRelocatingShards(true)
        ).actionGet();
        assertThat(health.getStatus(), lessThanOrEqualTo(ClusterHealthStatus.YELLOW));
        assertThat("Cluster must be a single node cluster", health.getNumberOfDataNodes(), equalTo(1));
        IndicesService instanceFromNode = getInstanceFromNode(IndicesService.class);
        return instanceFromNode.indexServiceSafe(resolveIndex(index));
    }
    public Index resolveIndex(String index) {
        GetIndexResponse getIndexResponse = indicesAdmin().prepareGetIndex().setIndices(index).get();
        assertTrue("index " + index + " not found", getIndexResponse.getSettings().containsKey(index));
        String uuid = getIndexResponse.getSettings().get(index).get(IndexMetadata.SETTING_INDEX_UUID);
        return new Index(index, uuid);
    }
    /**
     * Create a new search context.
     */
    protected SearchContext createSearchContext(IndexService indexService) {
        return new TestSearchContext(indexService);
    }
    /**