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
searcherSupplier.close();
                    throw e;
                }
                return createAndPutReaderContext(request, indexService, shard, searcherSupplier, defaultKeepAlive);
            }
        } else {
            final long keepAliveInMillis = getKeepAlive(request);
            final IndexService indexService = indicesService.indexServiceSafe(request.shardId().getIndex());
            final IndexShard shard = indexService.getShard(request.shardId().id());
            final Engine.SearcherSupplier searcherSupplier = shard.acquireSearcherSupplier();
            return createAndPutReaderContext(request, indexService, shard, searcherSupplier, keepAliveInMillis);
        }
    }
    final ReaderContext createAndPutReaderContext(
        ShardSearchRequest request,
        IndexService indexService,
        IndexShard shard,
        Engine.SearcherSupplier reader,
        long keepAliveInMillis
    ) {
        ReaderContext readerContext = null;
        Releasable decreaseScrollContexts = null;
        try {
            if (request.scroll() != null) {
                decreaseScrollContexts = openScrollContexts::decrementAndGet;
                if (openScrollContexts.incrementAndGet() > maxOpenScrollContext) {
                    throw new TooManyScrollContextsException(maxOpenScrollContext, MAX_OPEN_SCROLL_CONTEXT.getKey());
                }
            }
            final ShardSearchContextId id = new ShardSearchContextId(sessionId, idGenerator.incrementAndGet());