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
builder.put(MergeSchedulerConfig.MAX_THREAD_COUNT_SETTING.getKey(), maxThreadCount);
            }
        }
        return builder;
    }
    private static Settings.Builder setRandomIndexTranslogSettings(Random random, Settings.Builder builder) {
        if (random.nextBoolean()) {
            builder.put(
                IndexSettings.INDEX_TRANSLOG_FLUSH_THRESHOLD_SIZE_SETTING.getKey(),
                new ByteSizeValue(RandomNumbers.randomIntBetween(random, 1, 300), ByteSizeUnit.MB)
            );
        }
        if (random.nextBoolean()) {
            builder.put(IndexSettings.INDEX_TRANSLOG_FLUSH_THRESHOLD_SIZE_SETTING.getKey(), new ByteSizeValue(1, ByteSizeUnit.PB)); 
                                                                                                                                    
                                                                                                                                    
        }
        if (random.nextBoolean()) {
            builder.put(
                IndexSettings.INDEX_TRANSLOG_DURABILITY_SETTING.getKey(),
                RandomPicks.randomFrom(random, Translog.Durability.values())
            );
        }
        if (random.nextBoolean()) {
            builder.put(
                IndexSettings.INDEX_TRANSLOG_SYNC_INTERVAL_SETTING.getKey(),
                RandomNumbers.randomIntBetween(random, 100, 5000),
                TimeUnit.MILLISECONDS
            );
        }