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 final void createIndex(String name, int shards, int replicas) {
        createIndex(name, indexSettings(shards, replicas).build());
    }
    /**
     * Creates a new {@link CreateIndexRequestBuilder} with the settings obtained from {@link #indexSettings()}.
     */
    public final CreateIndexRequestBuilder prepareCreate(String index) {
        return prepareCreate(index, -1);
    }
    /**
     * Creates a new {@link CreateIndexRequestBuilder} with the settings obtained from {@link #indexSettings()}.
     * The index that is created with this builder will only be allowed to allocate on the number of nodes passed to this
     * method.
     * <p>
     * This method uses allocation deciders to filter out certain nodes to allocate the created index on. It defines allocation
     * rules based on <code>index.routing.allocation.exclude._name</code>.
     * </p>
     */
    public final CreateIndexRequestBuilder prepareCreate(String index, int numNodes) {
        return prepareCreate(index, numNodes, Settings.builder());
    }
    /**
     * Creates a new {@link CreateIndexRequestBuilder} with the settings obtained from {@link #indexSettings()}, augmented
     * by the given builder
     */
    public CreateIndexRequestBuilder prepareCreate(String index, Settings.Builder settingsBuilder) {
        return prepareCreate(index, -1, settingsBuilder);
    }
    /**
     * Creates a new {@link CreateIndexRequestBuilder} with the settings obtained from {@link #indexSettings()}.