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
public static String resolveCustomDataPath(String index) {
        GetIndexResponse getIndexResponse = indicesAdmin().prepareGetIndex().setIndices(index).get();
        assertTrue("index " + index + " not found", getIndexResponse.getSettings().containsKey(index));
        return getIndexResponse.getSettings().get(index).get(IndexMetadata.SETTING_DATA_PATH);
    }
    public static boolean inFipsJvm() {
        return Boolean.parseBoolean(System.getProperty(FIPS_SYSPROP));
    }
    protected void restartNodesOnBrokenClusterState(ClusterState.Builder clusterStateBuilder) throws Exception {
        Map<String, PersistedClusterStateService> lucenePersistedStateFactories = Stream.of(internalCluster().getNodeNames())
            .collect(
                Collectors.toMap(
                    Function.identity(),
                    nodeName -> internalCluster().getInstance(PersistedClusterStateService.class, nodeName)
                )
            );
        final ClusterState clusterState = clusterStateBuilder.build();
        internalCluster().fullRestart(new InternalTestCluster.RestartCallback() {
            @Override
            public Settings onNodeStopped(String nodeName) throws Exception {
                final PersistedClusterStateService lucenePersistedStateFactory = lucenePersistedStateFactories.get(nodeName);
                try (PersistedClusterStateService.Writer writer = lucenePersistedStateFactory.createWriter()) {
                    writer.writeFullStateAndCommit(clusterState.term(), clusterState);
                }
                return super.onNodeStopped(nodeName);
            }
        });
    }
}