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
case SUITE -> {
                assert SUITE_SEED != null : "Suite seed was not initialized";
                currentCluster = buildAndPutCluster(currentClusterScope, SUITE_SEED);
                RandomizedContext.current().runWithPrivateRandomness(SUITE_SEED, setup);
            }
            case TEST -> {
                currentCluster = buildAndPutCluster(currentClusterScope, randomLong());
                setup.call();
            }
        }
    }
    private void printTestMessage(String message) {
        if (isSuiteScopedTest(getClass()) && (getTestName().equals("<unknown>"))) {
            logger.info("[{}]: {} suite", getTestClass().getSimpleName(), message);
        } else {
            logger.info("[{}#{}]: {} test", getTestClass().getSimpleName(), getTestName(), message);
        }
    }
    /**
     * Creates a randomized index template. This template is used to pass in randomized settings on a
     * per index basis. Allows to enable/disable the randomization for number of shards and replicas
     */
    private void randomIndexTemplate() {
        
        if (cluster().size() > 0) {
            Settings.Builder randomSettingsBuilder = setRandomIndexSettings(random(), Settings.builder());
            if (isInternalCluster()) {
                
                randomSettingsBuilder.put(INDEX_TEST_SEED_SETTING.getKey(), random().nextLong());
            }