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
}, timeout, EsExecutors.DIRECT_EXECUTOR_SERVICE);
            
            
            final boolean allowWaitForNotYetIssued = shard.routingEntry().isPromotableToPrimary() == false
                && NO_TIMEOUT.equals(timeout) == false
                && timeout.getSeconds() <= 30L;
            shard.addRefreshListener(waitForCheckpoint, allowWaitForNotYetIssued, new ActionListener<>() {
                @Override
                public void onResponse(Void unused) {
                    
                    
                    if (shard.getLastKnownGlobalCheckpoint() >= waitForCheckpoint) {
                        searchReady();
                        return;
                    }
                    shard.addGlobalCheckpointListener(waitForCheckpoint, new GlobalCheckpointListeners.GlobalCheckpointListener() {
                        @Override
                        public Executor executor() {
                            return EsExecutors.DIRECT_EXECUTOR_SERVICE;
                        }
                        @Override
                        public void accept(long g, Exception e) {
                            if (g != UNASSIGNED_SEQ_NO) {
                                assert waitForCheckpoint <= g
                                    : shard.shardId() + " only advanced to [" + g + "] while waiting for [" + waitForCheckpoint + "]";
                                searchReady();
                            } else {
                                assert e != null;
                                
                                if (e instanceof TimeoutException == false) {