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
* Prints the current cluster state as debug logging.
     */
    public void logClusterState() {
        logger.debug(
            "cluster state:\n{}\n{}",
            clusterAdmin().prepareState().get().getState(),
            clusterAdmin().preparePendingClusterTasks().get()
        );
    }
    protected void ensureClusterSizeConsistency() {
        if (cluster() != null && cluster().size() > 0) { 
            logger.trace("Check consistency for [{}] nodes", cluster().size());
            assertNoTimeout(clusterAdmin().prepareHealth().setWaitForNodes(Integer.toString(cluster().size())).get());
        }
    }
    /**
     * Verifies that all nodes that have the same version of the cluster state as master have same cluster state
     */
    protected void ensureClusterStateConsistency() throws IOException {
        if (cluster() != null && cluster().size() > 0) {
            final NamedWriteableRegistry namedWriteableRegistry = cluster().getNamedWriteableRegistry();
            final Client masterClient = client();
            ClusterState masterClusterState = masterClient.admin().cluster().prepareState().all().get().getState();
            byte[] masterClusterStateBytes = ClusterState.Builder.toBytes(masterClusterState);
            
            masterClusterState = ClusterState.Builder.fromBytes(masterClusterStateBytes, null, namedWriteableRegistry);
            Map<String, Object> masterStateMap = convertToMap(masterClusterState);
            int masterClusterStateSize = ClusterState.Builder.toBytes(masterClusterState).length;
            String masterId = masterClusterState.nodes().getMasterNodeId();
            for (Client client : cluster().getClients()) {