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
latches.add(l);
        return l;
    }
    /**
     * Maybe refresh, force merge, or flush then always make sure there aren't too many in flight async operations.
     */
    private void postIndexAsyncActions(String[] indices, List<CountDownLatch> inFlightAsyncOperations, boolean maybeFlush)
        throws InterruptedException {
        if (rarely()) {
            if (rarely()) {
                indicesAdmin().prepareRefresh(indices)
                    .setIndicesOptions(IndicesOptions.lenientExpandOpen())
                    .execute(new LatchedActionListener<>(newLatch(inFlightAsyncOperations)));
            } else if (maybeFlush && rarely()) {
                indicesAdmin().prepareFlush(indices)
                    .setIndicesOptions(IndicesOptions.lenientExpandOpen())
                    .execute(new LatchedActionListener<>(newLatch(inFlightAsyncOperations)));
            } else if (rarely()) {
                indicesAdmin().prepareForceMerge(indices)
                    .setIndicesOptions(IndicesOptions.lenientExpandOpen())
                    .setMaxNumSegments(between(1, 10))
                    .setFlush(maybeFlush && randomBoolean())
                    .execute(new LatchedActionListener<>(newLatch(inFlightAsyncOperations)));
            }
        }
        while (inFlightAsyncOperations.size() > MAX_IN_FLIGHT_ASYNC_INDEXES) {
            int waitFor = between(0, inFlightAsyncOperations.size() - 1);
            inFlightAsyncOperations.remove(waitFor).await();
        }
    }