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
private final CopyOnWriteArrayList<Tuple<T, Exception>> errors;
        private final T builder;
        PayloadLatchedActionListener(T builder, CountDownLatch latch, CopyOnWriteArrayList<Tuple<T, Exception>> errors) {
            super(latch);
            this.errors = errors;
            this.builder = builder;
        }
        @Override
        protected void addError(Exception e) {
            errors.add(new Tuple<>(builder, e));
        }
    }
    /**
     * Clears the given scroll Ids
     */
    public void clearScroll(String... scrollIds) {
        ClearScrollResponse clearResponse = client().prepareClearScroll().setScrollIds(Arrays.asList(scrollIds)).get();
        assertThat(clearResponse.isSucceeded(), equalTo(true));
    }
    private static <A extends Annotation> A getAnnotation(Class<?> clazz, Class<A> annotationClass) {
        if (clazz == Object.class || clazz == ESIntegTestCase.class) {
            return null;
        }
        A annotation = clazz.getAnnotation(annotationClass);
        if (annotation != null) {
            return annotation;
        }