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
}));
    }
    private Executor getExecutor(IndexShard indexShard) {
        assert indexShard != null;
        final String executorName;
        if (indexShard.isSystem()) {
            executorName = executorSelector.executorForSearch(indexShard.shardId().getIndexName());
        } else if (indexShard.indexSettings().isSearchThrottled()) {
            executorName = Names.SEARCH_THROTTLED;
        } else {
            executorName = Names.SEARCH;
        }
        return threadPool.executor(executorName);
    }
    public void executeFetchPhase(
        InternalScrollSearchRequest request,
        SearchShardTask task,
        ActionListener<ScrollQueryFetchSearchResult> listener
    ) {
        final LegacyReaderContext readerContext = (LegacyReaderContext) findReaderContext(request.contextId(), request);
        final Releasable markAsUsed;
        try {
            markAsUsed = readerContext.markAsUsed(getScrollKeepAlive(request.scroll()));
        } catch (Exception e) {
            
            freeReaderContext(readerContext.id());
            throw e;
        }
        runAsync(getExecutor(readerContext.indexShard()), () -> {
            final ShardSearchRequest shardSearchRequest = readerContext.getShardSearchRequest(null);