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
protected int numberOfReplicas() {
        return between(minimumNumberOfReplicas(), maximumNumberOfReplicas());
    }
    public void setDisruptionScheme(ServiceDisruptionScheme scheme) {
        internalCluster().setDisruptionScheme(scheme);
    }
    /**
     * Creates a disruption that isolates the current master node from all other nodes in the cluster.
     *
     * @param disruptionType type of disruption to create
     * @return disruption
     */
    protected static NetworkDisruption isolateMasterDisruption(NetworkDisruption.NetworkLinkDisruptionType disruptionType) {
        final String masterNode = internalCluster().getMasterName();
        return new NetworkDisruption(
            new NetworkDisruption.TwoPartitions(
                Collections.singleton(masterNode),
                Arrays.stream(internalCluster().getNodeNames()).filter(name -> name.equals(masterNode) == false).collect(Collectors.toSet())
            ),
            disruptionType
        );
    }
    /**
     * Returns a settings object used in {@link #createIndex(String...)} and {@link #prepareCreate(String)} and friends.
     * This method can be overwritten by subclasses to set defaults for the indices that are created by the test.
     * By default it returns a settings object that sets a random number of shards. Number of shards and replicas
     * can be controlled through specific methods.
     */
    public Settings indexSettings() {
        Settings.Builder builder = Settings.builder();