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
}
        return actionGet.getStatus();
    }
    /**
     * Waits until at least a give number of document is visible for searchers
     *
     * @param numDocs number of documents to wait for
     * @param indexer a {@link org.elasticsearch.test.BackgroundIndexer}. It will be first checked for documents indexed.
     *                This saves on unneeded searches.
     */
    public void waitForDocs(final long numDocs, final BackgroundIndexer indexer) throws Exception {
        
        final long maxWaitTimeMs = Math.max(90 * 1000, 200 * numDocs);
        assertBusy(() -> {
            long lastKnownCount = indexer.totalIndexedDocs();
            if (lastKnownCount >= numDocs) {
                try {
                    long count = prepareSearch().setTrackTotalHits(true)
                        .setSize(0)
                        .setQuery(matchAllQuery())
                        .get()
                        .getHits()
                        .getTotalHits().value;
                    if (count == lastKnownCount) {
                        
                        indicesAdmin().prepareRefresh().get();
                    }
                    lastKnownCount = count;
                } catch (Exception e) { 
                    logger.debug("failed to executed count", e);