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
server/src/main/java/org/elasticsearch/search/SearchService.java
}
        SearchShardTarget shardTarget = context.shardTarget();
        SearchExecutionContext searchExecutionContext = context.getSearchExecutionContext();
        context.from(source.from());
        context.size(source.size());
        Map<String, InnerHitContextBuilder> innerHitBuilders = new HashMap<>();
        QueryBuilder query = source.query();
        if (query != null) {
            InnerHitContextBuilder.extractInnerHits(query, innerHitBuilders);
            context.parsedQuery(searchExecutionContext.toQuery(query));
        }
        if (source.postFilter() != null) {
            InnerHitContextBuilder.extractInnerHits(source.postFilter(), innerHitBuilders);
            context.parsedPostFilter(searchExecutionContext.toQuery(source.postFilter()));
        }
        if (innerHitBuilders.size() > 0) {
            for (Map.Entry<String, InnerHitContextBuilder> entry : innerHitBuilders.entrySet()) {
                try {
                    entry.getValue().build(context, context.innerHits());
                } catch (IOException e) {
                    throw new SearchException(shardTarget, "failed to build inner_hits", e);
                }
            }
        }
        if (source.sorts() != null) {
            try {
                Optional<SortAndFormats> optionalSort = SortBuilder.buildSort(source.sorts(), context.getSearchExecutionContext());
                if (optionalSort.isPresent()) {
                    context.sort(optionalSort.get());
                }