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
rewriteAndFetchShardRequest(readerContext.indexShard(), shardSearchRequest, listener.delegateFailure((l, rewritten) -> {
            
            runAsync(getExecutor(readerContext.indexShard()), () -> {
                readerContext.setAggregatedDfs(request.dfs());
                try (
                    SearchContext searchContext = createContext(readerContext, shardSearchRequest, task, ResultsType.QUERY, true);
                    SearchOperationListenerExecutor executor = new SearchOperationListenerExecutor(searchContext)
                ) {
                    searchContext.searcher().setAggregatedDfs(request.dfs());
                    QueryPhase.execute(searchContext);
                    if (searchContext.queryResult().hasSearchContext() == false && readerContext.singleSession()) {
                        
                        freeReaderContext(readerContext.id());
                    }
                    executor.success();
                    
                    
                    
                    final RescoreDocIds rescoreDocIds = searchContext.rescoreDocIds();
                    searchContext.queryResult().setRescoreDocIds(rescoreDocIds);
                    readerContext.setRescoreDocIds(rescoreDocIds);
                    searchContext.queryResult().incRef();
                    return searchContext.queryResult();
                } catch (Exception e) {
                    assert TransportActions.isShardNotAvailableException(e) == false : new AssertionError(e);
                    logger.trace("Query phase failed", e);
                    
                    throw e;
                }
            }, wrapFailureListener(l, readerContext, markAsUsed));