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
* Returns {@code true} if this test cluster can use a mock internal engine. Defaults to true.
     */
    protected boolean addMockInternalEngine() {
        return true;
    }
    /**
     * Returns {@code true} if this test cluster can use the {@link MockFSIndexStore} test plugin. Defaults to true.
     */
    protected boolean addMockFSIndexStore() {
        return true;
    }
    /**
     * Returns a function that allows to wrap / filter all clients that are exposed by the test cluster. This is useful
     * for debugging or request / response pre and post processing. It also allows to intercept all calls done by the test
     * framework. By default this method returns an identity function {@link Function#identity()}.
     */
    protected Function<Client, Client> getClientWrapper() {
        return Function.identity();
    }
    
    protected Collection<Class<? extends Plugin>> getMockPlugins() {
        final ArrayList<Class<? extends Plugin>> mocks = new ArrayList<>();
        if (MOCK_MODULES_ENABLED && randomBoolean()) { 
            if (randomBoolean() && addMockTransportService()) {
                mocks.add(MockTransportService.TestPlugin.class);
            }
            if (addMockFSIndexStore() && randomBoolean()) {
                mocks.add(MockFSIndexStore.TestPlugin.class);
            }
            if (randomBoolean()) {