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
if (request.scroll() != null) {
                readerContext = new LegacyReaderContext(id, indexService, shard, reader, request, keepAliveInMillis);
                if (request.scroll() != null) {
                    readerContext.addOnClose(decreaseScrollContexts);
                    decreaseScrollContexts = null;
                }
            } else {
                readerContext = new ReaderContext(id, indexService, shard, reader, keepAliveInMillis, true);
            }
            reader = null;
            final ReaderContext finalReaderContext = readerContext;
            final SearchOperationListener searchOperationListener = shard.getSearchOperationListener();
            searchOperationListener.onNewReaderContext(finalReaderContext);
            if (finalReaderContext.scrollContext() != null) {
                searchOperationListener.onNewScrollContext(finalReaderContext);
            }
            readerContext.addOnClose(() -> {
                try {
                    if (finalReaderContext.scrollContext() != null) {
                        searchOperationListener.onFreeScrollContext(finalReaderContext);
                    }
                } finally {
                    searchOperationListener.onFreeReaderContext(finalReaderContext);
                }
            });
            putReaderContext(finalReaderContext);
            readerContext = null;
            return finalReaderContext;
        } finally {
            Releasables.close(reader, readerContext, decreaseScrollContexts);