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
* system without asserting modules that to make sure they don't hide any bugs in
     * production.
     *
     * @see ESIntegTestCase
     */
    public static final String TESTS_ENABLE_MOCK_MODULES = "tests.enable_mock_modules";
    private static final boolean MOCK_MODULES_ENABLED = "true".equals(System.getProperty(TESTS_ENABLE_MOCK_MODULES, "true"));
    /**
     * Threshold at which indexing switches from frequently async to frequently bulk.
     */
    private static final int FREQUENT_BULK_THRESHOLD = 300;
    /**
     * Threshold at which bulk indexing will always be used.
     */
    private static final int ALWAYS_BULK_THRESHOLD = 3000;
    /**
     * Maximum number of async operations that indexRandom will kick off at one time.
     */
    private static final int MAX_IN_FLIGHT_ASYNC_INDEXES = 150;
    /**
     * Maximum number of documents in a single bulk index request.
     */
    private static final int MAX_BULK_INDEX_REQUEST_SIZE = 1000;
    /**
     * Default minimum number of shards for an index
     */
    protected static final int DEFAULT_MIN_NUM_SHARDS = 1;
    /**
     * Default maximum number of shards for an index
     */