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
context.close();
            throw e;
        }
        return context;
    }
    public DefaultSearchContext createSearchContext(ShardSearchRequest request, TimeValue timeout) throws IOException {
        final IndexService indexService = indicesService.indexServiceSafe(request.shardId().getIndex());
        final IndexShard indexShard = indexService.getShard(request.shardId().getId());
        final Engine.SearcherSupplier reader = indexShard.acquireSearcherSupplier();
        final ShardSearchContextId id = new ShardSearchContextId(sessionId, idGenerator.incrementAndGet());
        try (ReaderContext readerContext = new ReaderContext(id, indexService, indexShard, reader, -1L, true)) {
            DefaultSearchContext searchContext = createSearchContext(readerContext, request, timeout, ResultsType.NONE);
            searchContext.addReleasable(readerContext.markAsUsed(0L));
            return searchContext;
        }
    }
    @SuppressWarnings("unchecked")
    private DefaultSearchContext createSearchContext(
        ReaderContext reader,
        ShardSearchRequest request,
        TimeValue timeout,
        ResultsType resultsType
    ) throws IOException {
        boolean success = false;
        DefaultSearchContext searchContext = null;
        try {
            SearchShardTarget shardTarget = new SearchShardTarget(
                clusterService.localNode().getId(),
                reader.indexShard().shardId(),
                request.getClusterAlias()