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
test/framework/src/main/java/org/elasticsearch/test/ESIntegTestCase.java
ClusterState localClusterState = client.admin().cluster().prepareState().all().setLocal(true).get().getState();
                byte[] localClusterStateBytes = ClusterState.Builder.toBytes(localClusterState);
                
                localClusterState = ClusterState.Builder.fromBytes(localClusterStateBytes, null, namedWriteableRegistry);
                final Map<String, Object> localStateMap = convertToMap(localClusterState);
                final int localClusterStateSize = ClusterState.Builder.toBytes(localClusterState).length;
                
                
                if (masterClusterState.version() == localClusterState.version()
                    && masterId.equals(localClusterState.nodes().getMasterNodeId())) {
                    try {
                        assertEquals("cluster state UUID does not match", masterClusterState.stateUUID(), localClusterState.stateUUID());
                        
                        
                        assertEquals("cluster state size does not match", masterClusterStateSize, localClusterStateSize);
                        
                        assertNull(
                            "cluster state JSON serialization does not match",
                            differenceBetweenMapsIgnoringArrayOrder(masterStateMap, localStateMap)
                        );
                    } catch (final AssertionError error) {
                        logger.error(
                            "Cluster state from master:\n{}\nLocal cluster state:\n{}",
                            masterClusterState.toString(),
                            localClusterState.toString()
                        );
                        throw error;
                    }
                }
            }