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 final Map<Long, ReaderContext> activeReaders = ConcurrentCollections.newConcurrentMapWithAggressiveConcurrency();
    private final MultiBucketConsumerService multiBucketConsumerService;
    private final AtomicInteger openScrollContexts = new AtomicInteger();
    private final String sessionId = UUIDs.randomBase64UUID();
    private final Tracer tracer;
    public SearchService(
        ClusterService clusterService,
        IndicesService indicesService,
        ThreadPool threadPool,
        ScriptService scriptService,
        BigArrays bigArrays,
        FetchPhase fetchPhase,
        ResponseCollectorService responseCollectorService,
        CircuitBreakerService circuitBreakerService,
        ExecutorSelector executorSelector,
        Tracer tracer
    ) {
        Settings settings = clusterService.getSettings();
        this.threadPool = threadPool;
        this.clusterService = clusterService;
        this.indicesService = indicesService;
        this.scriptService = scriptService;
        this.responseCollectorService = responseCollectorService;
        this.bigArrays = bigArrays;
        this.fetchPhase = fetchPhase;
        this.multiBucketConsumerService = new MultiBucketConsumerService(
            clusterService,
            settings,
            circuitBreakerService.getBreaker(CircuitBreaker.REQUEST)
        );