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
.subSearches()
                .stream()
                .anyMatch(sqwb -> sqwb.getQueryBuilder() instanceof MatchNoneQueryBuilder == false);
        }
        return canMatch;
    }
    /**
     * Returns true iff the given search source builder can be early terminated by rewriting to a match none query. Or in other words
     * if the execution of the search request can be early terminated without executing it. This is for instance not possible if
     * a global aggregation is part of this request or if there is a suggest builder present.
     */
    public static boolean canRewriteToMatchNone(SearchSourceBuilder source) {
        if (source == null || source.suggest() != null) {
            return false;
        }
        if (source.subSearches().isEmpty()
            || source.subSearches().stream().anyMatch(sqwb -> sqwb.getQueryBuilder() instanceof MatchAllQueryBuilder)) {
            return false;
        }
        AggregatorFactories.Builder aggregations = source.aggregations();
        return aggregations == null || aggregations.mustVisitAllDocs() == false;
    }
    @SuppressWarnings({ "rawtypes", "unchecked" })
    private void rewriteAndFetchShardRequest(IndexShard shard, ShardSearchRequest request, ActionListener<ShardSearchRequest> listener) {
        ActionListener<Rewriteable> actionListener = listener.delegateFailureAndWrap((l, r) -> {
            if (request.readerId() != null) {
                l.onResponse(request);
            } else {
                shard.ensureShardSearchActive(b -> l.onResponse(request));
            }