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
BulkResponse actionGet = bulkBuilder.execute().actionGet();
                assertThat(actionGet.hasFailures() ? actionGet.buildFailureMessage() : "", actionGet.hasFailures(), equalTo(false));
            }
        }
        for (CountDownLatch operation : inFlightAsyncOperations) {
            operation.await();
        }
        final List<Exception> actualErrors = new ArrayList<>();
        for (Tuple<IndexRequestBuilder, Exception> tuple : errors) {
            Throwable t = ExceptionsHelper.unwrapCause(tuple.v2());
            if (t instanceof EsRejectedExecutionException) {
                logger.debug("Error indexing doc: " + t.getMessage() + ", reindexing.");
                tuple.v1().execute().actionGet(); 
            } else {
                actualErrors.add(tuple.v2());
            }
        }
        assertThat(actualErrors, emptyIterable());
        if (bogusIds.isEmpty() == false) {
            
            for (List<String> doc : bogusIds) {
                assertEquals(
                    "failed to delete a dummy doc [" + doc.get(0) + "][" + doc.get(1) + "]",
                    DocWriteResponse.Result.DELETED,
                    client().prepareDelete(doc.get(0), doc.get(1)).setRouting(doc.get(1)).get().getResult()
                );
            }
        }
        if (forceRefresh) {
            assertNoFailures(indicesAdmin().prepareRefresh(indicesArray).setIndicesOptions(IndicesOptions.lenientExpandOpen()).get());