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
List<CountDownLatch> inFlightAsyncOperations = new ArrayList<>();
        
        final String[] indicesArray = indices.toArray(new String[] {});
        if (builders.size() < FREQUENT_BULK_THRESHOLD ? frequently() : builders.size() < ALWAYS_BULK_THRESHOLD ? rarely() : false) {
            if (frequently()) {
                logger.info("Index [{}] docs async: [{}] bulk: [{}]", builders.size(), true, false);
                for (IndexRequestBuilder indexRequestBuilder : builders) {
                    indexRequestBuilder.execute(
                        new PayloadLatchedActionListener<>(indexRequestBuilder, newLatch(inFlightAsyncOperations), errors)
                    );
                    postIndexAsyncActions(indicesArray, inFlightAsyncOperations, maybeFlush);
                }
            } else {
                logger.info("Index [{}] docs async: [{}] bulk: [{}]", builders.size(), false, false);
                for (IndexRequestBuilder indexRequestBuilder : builders) {
                    indexRequestBuilder.execute().actionGet();
                    postIndexAsyncActions(indicesArray, inFlightAsyncOperations, maybeFlush);
                }
            }
        } else {
            List<List<IndexRequestBuilder>> partition = eagerPartition(
                builders,
                Math.min(MAX_BULK_INDEX_REQUEST_SIZE, Math.max(1, (int) (builders.size() * randomDouble())))
            );
            logger.info("Index [{}] docs async: [{}] bulk: [{}] partitions [{}]", builders.size(), false, true, partition.size());
            for (List<IndexRequestBuilder> segmented : partition) {
                BulkRequestBuilder bulkBuilder = client().prepareBulk();
                for (IndexRequestBuilder indexRequestBuilder : segmented) {
                    bulkBuilder.add(indexRequestBuilder);
                }