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/ESSingleNodeTestCase.java
* This method returns <code>true</code> if the node that is used in the background should be reset
     * after each test. This is useful if the test changes the cluster state metadata etc. The default is
     * <code>false</code>.
     */
    protected boolean resetNodeAfterTest() {
        return false;
    }
    
    protected Collection<Class<? extends Plugin>> getPlugins() {
        return Collections.emptyList();
    }
    
    @SafeVarargs
    @SuppressWarnings("varargs") 
    protected final Collection<Class<? extends Plugin>> pluginList(Class<? extends Plugin>... plugins) {
        return Arrays.asList(plugins);
    }
    
    protected Settings nodeSettings() {
        return Settings.EMPTY;
    }
    
    protected boolean addMockHttpTransport() {
        return true;
    }
    @Override
    protected List<String> filteredWarnings() {
        return Stream.concat(
            super.filteredWarnings().stream(),
            Stream.of("[index.data_path] setting was deprecated in Elasticsearch and will be removed in a future release.")