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
);
            ExecutorService executor = this.enableSearchWorkerThreads ? threadPool.executor(Names.SEARCH_WORKER) : null;
            int maximumNumberOfSlices = determineMaximumNumberOfSlices(executor, request, resultsType);
            searchContext = new DefaultSearchContext(
                reader,
                request,
                shardTarget,
                threadPool::relativeTimeInMillis,
                timeout,
                fetchPhase,
                lowLevelCancellation,
                executor,
                maximumNumberOfSlices,
                minimumDocsPerSlice
            );
            
            
            
            SearchExecutionContext context = new SearchExecutionContext(searchContext.getSearchExecutionContext());
            Rewriteable.rewrite(request.getRewriteable(), context, true);
            assert searchContext.getSearchExecutionContext().isCacheable();
            success = true;
        } finally {
            if (success == false) {
                
                
                
                IOUtils.closeWhileHandlingException(searchContext);
            }
        }