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/ESSingleNodeTestCase.java
).collect(Collectors.toList());
    }
    private Node newNode() {
        final Path tempDir = createTempDir();
        final String nodeName = nodeSettings().get(Node.NODE_NAME_SETTING.getKey(), "node_s_0");
        Settings.Builder settingBuilder = Settings.builder()
            .put(ClusterName.CLUSTER_NAME_SETTING.getKey(), InternalTestCluster.clusterName("single-node-cluster", random().nextLong()))
            .put(DestructiveOperations.REQUIRES_NAME_SETTING.getKey(), false)
            .put(Environment.PATH_HOME_SETTING.getKey(), tempDir)
            .put(Environment.PATH_REPO_SETTING.getKey(), tempDir.resolve("repo"))
            
            
            .put(Environment.PATH_SHARED_DATA_SETTING.getKey(), createTempDir().getParent())
            .put(Node.NODE_NAME_SETTING.getKey(), nodeName)
            .put(EsExecutors.NODE_PROCESSORS_SETTING.getKey(), 1) 
            .put("transport.type", getTestTransportType())
            .put(TransportSettings.PORT.getKey(), ESTestCase.getPortRange())
            .put(dataNode())
            .put(NodeEnvironment.NODE_ID_SEED_SETTING.getKey(), random().nextLong())
            
            .put(DiskThresholdSettings.CLUSTER_ROUTING_ALLOCATION_LOW_DISK_WATERMARK_SETTING.getKey(), "1b")
            .put(DiskThresholdSettings.CLUSTER_ROUTING_ALLOCATION_HIGH_DISK_WATERMARK_SETTING.getKey(), "1b")
            .put(DiskThresholdSettings.CLUSTER_ROUTING_ALLOCATION_DISK_FLOOD_STAGE_WATERMARK_SETTING.getKey(), "1b")
            
            
            .put(HierarchyCircuitBreakerService.USE_REAL_MEMORY_USAGE_SETTING.getKey(), false)
            .putList(DISCOVERY_SEED_HOSTS_SETTING.getKey()) 
            .putList(INITIAL_MASTER_NODES_SETTING.getKey(), nodeName)
            .put(nodeSettings());
        boolean enableConcurrentSearch = enableConcurrentSearch();