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
return tasks.tasks().stream().filter(t -> taskNames.contains(t.getTaskName())).toList();
    }
    /**
     * Waits for the health node to be assigned and returns the node
     * that it is assigned to.
     * Returns null if the health node is not assigned in due time.
     */
    @Nullable
    public static DiscoveryNode waitAndGetHealthNode(InternalTestCluster internalCluster) {
        DiscoveryNode[] healthNode = new DiscoveryNode[1];
        try {
            waitUntil(() -> {
                ClusterState state = internalCluster.client()
                    .admin()
                    .cluster()
                    .prepareState()
                    .clear()
                    .setMetadata(true)
                    .setNodes(true)
                    .get()
                    .getState();
                healthNode[0] = HealthNode.findHealthNode(state);
                return healthNode[0] != null;
            }, 15, TimeUnit.SECONDS);
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
        }
        return healthNode[0];
    }
    /**