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
searcher = searcherSupplier.acquireSearcher(Engine.CAN_MATCH_SEARCH_SOURCE);
                }
                canMatchSearcher = searcher;
            } else {
                indexService = indicesService.indexServiceSafe(request.shardId().getIndex());
                if (canMatchAfterRewrite(request, indexService) == false) {
                    return new CanMatchShardResponse(false, null);
                }
                IndexShard indexShard = indexService.getShard(request.shardId().getId());
                boolean needsWaitForRefresh = request.waitForCheckpoint() != UNASSIGNED_SEQ_NO;
                
                
                
                hasRefreshPending = needsWaitForRefresh || (indexShard.hasRefreshPending() && checkRefreshPending);
                canMatchSearcher = indexShard.acquireSearcher(Engine.CAN_MATCH_SEARCH_SOURCE);
            }
            try (canMatchSearcher) {
                SearchExecutionContext context = indexService.newSearchExecutionContext(
                    request.shardId().id(),
                    0,
                    canMatchSearcher,
                    request::nowInMillis,
                    request.getClusterAlias(),
                    request.getRuntimeMappings()
                );
                final boolean canMatch = queryStillMatchesAfterRewrite(request, context);
                final MinAndMax<?> minMax;
                if (canMatch || hasRefreshPending) {
                    FieldSortBuilder sortBuilder = FieldSortBuilder.getPrimaryFieldSortOrNull(request.source());
                    minMax = sortBuilder != null ? FieldSortBuilder.getMinMaxOrNull(context, sortBuilder) : null;