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
this.executorSelector = executorSelector;
        this.tracer = tracer;
        TimeValue keepAliveInterval = KEEPALIVE_INTERVAL_SETTING.get(settings);
        setKeepAlives(DEFAULT_KEEPALIVE_SETTING.get(settings), MAX_KEEPALIVE_SETTING.get(settings));
        clusterService.getClusterSettings()
            .addSettingsUpdateConsumer(
                DEFAULT_KEEPALIVE_SETTING,
                MAX_KEEPALIVE_SETTING,
                this::setKeepAlives,
                SearchService::validateKeepAlives
            );
        this.keepAliveReaper = threadPool.scheduleWithFixedDelay(new Reaper(), keepAliveInterval, threadPool.executor(Names.SEARCH));
        defaultSearchTimeout = DEFAULT_SEARCH_TIMEOUT_SETTING.get(settings);
        clusterService.getClusterSettings().addSettingsUpdateConsumer(DEFAULT_SEARCH_TIMEOUT_SETTING, this::setDefaultSearchTimeout);
        minimumDocsPerSlice = MINIMUM_DOCS_PER_SLICE.get(settings);
        defaultAllowPartialSearchResults = DEFAULT_ALLOW_PARTIAL_SEARCH_RESULTS.get(settings);
        clusterService.getClusterSettings()
            .addSettingsUpdateConsumer(DEFAULT_ALLOW_PARTIAL_SEARCH_RESULTS, this::setDefaultAllowPartialSearchResults);
        maxOpenScrollContext = MAX_OPEN_SCROLL_CONTEXT.get(settings);
        clusterService.getClusterSettings().addSettingsUpdateConsumer(MAX_OPEN_SCROLL_CONTEXT, this::setMaxOpenScrollContext);
        lowLevelCancellation = LOW_LEVEL_CANCELLATION_SETTING.get(settings);
        clusterService.getClusterSettings().addSettingsUpdateConsumer(LOW_LEVEL_CANCELLATION_SETTING, this::setLowLevelCancellation);
        enableRewriteAggsToFilterByFilter = ENABLE_REWRITE_AGGS_TO_FILTER_BY_FILTER.get(settings);
        clusterService.getClusterSettings()
            .addSettingsUpdateConsumer(ENABLE_REWRITE_AGGS_TO_FILTER_BY_FILTER, this::setEnableRewriteAggsToFilterByFilter);
        enableSearchWorkerThreads = SEARCH_WORKER_THREADS_ENABLED.get(settings);
        clusterService.getClusterSettings().addSettingsUpdateConsumer(SEARCH_WORKER_THREADS_ENABLED, this::setEnableSearchWorkerThreads);
        enableQueryPhaseParallelCollection = QUERY_PHASE_PARALLEL_COLLECTION_ENABLED.get(settings);
        clusterService.getClusterSettings()
            .addSettingsUpdateConsumer(QUERY_PHASE_PARALLEL_COLLECTION_ENABLED, this::setEnableQueryPhaseParallelCollection);