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
String... indices
    ) {
        String color = clusterHealthStatus.name().toLowerCase(Locale.ROOT);
        String method = "ensure" + Strings.capitalize(color);
        ClusterHealthRequest healthRequest = new ClusterHealthRequest(indices).timeout(timeout)
            .waitForStatus(clusterHealthStatus)
            .waitForEvents(Priority.LANGUID)
            .waitForNoRelocatingShards(true)
            .waitForNoInitializingShards(waitForNoInitializingShards)
            
            
            
            
            
            
            
            .waitForNodes(Integer.toString(cluster().size()));
        final ClusterHealthResponse clusterHealthResponse = clusterAdmin().health(healthRequest).actionGet();
        if (clusterHealthResponse.isTimedOut()) {
            final var allocationExplainRef = new AtomicReference<ClusterAllocationExplainResponse>();
            final var clusterStateRef = new AtomicReference<ClusterStateResponse>();
            final var pendingTasksRef = new AtomicReference<PendingClusterTasksResponse>();
            final var hotThreadsRef = new AtomicReference<NodesHotThreadsResponse>();
            final var detailsFuture = new PlainActionFuture<Void>();
            try (var listeners = new RefCountingListener(detailsFuture)) {
                clusterAdmin().prepareAllocationExplain().execute(listeners.acquire(allocationExplainRef::set));
                clusterAdmin().prepareState().execute(listeners.acquire(clusterStateRef::set));
                clusterAdmin().preparePendingClusterTasks().execute(listeners.acquire(pendingTasksRef::set));
                clusterAdmin().prepareNodesHotThreads()
                    .setThreads(9999)