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
server/src/main/java/org/elasticsearch/search/SearchService.java
}
    }
    private QueryFetchSearchResult executeFetchPhase(ReaderContext reader, SearchContext context, long afterQueryTime) {
        try (
            Releasable scope = tracer.withScope(SpanId.forTask(context.getTask()));
            SearchOperationListenerExecutor executor = new SearchOperationListenerExecutor(context, true, afterQueryTime)
        ) {
            shortcutDocIdsToLoad(context);
            fetchPhase.execute(context);
            if (reader.singleSession()) {
                freeReaderContext(reader.id());
            }
            executor.success();
        }
        
        return new QueryFetchSearchResult(context.queryResult(), context.fetchResult());
    }
    public void executeQueryPhase(
        InternalScrollSearchRequest request,
        SearchShardTask task,
        ActionListener<ScrollQuerySearchResult> listener
    ) {
        final LegacyReaderContext readerContext = (LegacyReaderContext) findReaderContext(request.contextId(), request);
        final Releasable markAsUsed;
        try {
            markAsUsed = readerContext.markAsUsed(getScrollKeepAlive(request.scroll()));
        } catch (Exception e) {
            
            freeReaderContext(readerContext.id());
            throw e;