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 ClusterHealthStatus ensureGreen(String... indices) {
        return ensureGreen(TimeValue.timeValueSeconds(30), indices);
    }
    /**
     * Ensures the cluster has a green state via the cluster health API. This method will also wait for relocations.
     * It is useful to ensure that all action on the cluster have finished and all shards that were currently relocating
     * are now allocated and started.
     *
     * @param timeout time out value to set on {@link org.elasticsearch.action.admin.cluster.health.ClusterHealthRequest}
     */
    public ClusterHealthStatus ensureGreen(TimeValue timeout, String... indices) {
        return ensureColor(ClusterHealthStatus.GREEN, timeout, false, indices);
    }
    /**
     * Ensures the cluster has a yellow state via the cluster health API.
     */
    public ClusterHealthStatus ensureYellow(String... indices) {
        return ensureColor(ClusterHealthStatus.YELLOW, TimeValue.timeValueSeconds(30), false, indices);
    }
    /**
     * Ensures the cluster has a yellow state via the cluster health API and ensures the that cluster has no initializing shards
     * for the given indices
     */
    public ClusterHealthStatus ensureYellowAndNoInitializingShards(String... indices) {
        return ensureColor(ClusterHealthStatus.YELLOW, TimeValue.timeValueSeconds(30), true, indices);
    }
    private ClusterHealthStatus ensureColor(
        ClusterHealthStatus clusterHealthStatus,
        TimeValue timeout,
        boolean waitForNoInitializingShards,