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
.put(SearchService.LOW_LEVEL_CANCELLATION_SETTING.getKey(), randomBoolean())
            .putList(DISCOVERY_SEED_HOSTS_SETTING.getKey()) 
            .putList(DISCOVERY_SEED_PROVIDERS_SETTING.getKey(), "file")
            .put(
                TransportSearchAction.DEFAULT_PRE_FILTER_SHARD_SIZE.getKey(),
                randomFrom(1, 2, SearchRequest.DEFAULT_PRE_FILTER_SHARD_SIZE)
            );
        return builder.build();
    }
    protected Path nodeConfigPath(int nodeOrdinal) {
        return null;
    }
    /**
     * Returns a collection of plugins that should be loaded on each node.
     */
    protected Collection<Class<? extends Plugin>> nodePlugins() {
        return Collections.emptyList();
    }
    private ExternalTestCluster buildExternalCluster(String clusterAddresses, String clusterName) throws IOException {
        String[] stringAddresses = clusterAddresses.split(",");
        TransportAddress[] transportAddresses = new TransportAddress[stringAddresses.length];
        int i = 0;
        for (String stringAddress : stringAddresses) {
            URL url = new URL("http://" + stringAddress);
            InetAddress inetAddress = InetAddress.getByName(url.getHost());
            transportAddresses[i++] = new TransportAddress(new InetSocketAddress(inetAddress, url.getPort()));
        }
        return new ExternalTestCluster(
            createTempDir(),
            externalClusterClientSettings(),