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
public static final Setting<Integer> MINIMUM_DOCS_PER_SLICE = Setting.intSetting(
        "search.minimum_docs_per_slice",
        50_000,
        1,
        Property.NodeScope
    );
    public static final Setting<Boolean> SEARCH_WORKER_THREADS_ENABLED = Setting.boolSetting(
        "search.worker_threads_enabled",
        true,
        Property.NodeScope,
        Property.Dynamic
    );
    public static final Setting<Boolean> QUERY_PHASE_PARALLEL_COLLECTION_ENABLED = Setting.boolSetting(
        "search.query_phase_parallel_collection_enabled",
        false,
        Property.NodeScope,
        Property.Dynamic
    );
    public static final Setting<Integer> MAX_OPEN_SCROLL_CONTEXT = Setting.intSetting(
        "search.max_open_scroll_context",
        500,
        0,
        Property.Dynamic,
        Property.NodeScope
    );
    public static final Setting<Boolean> ENABLE_REWRITE_AGGS_TO_FILTER_BY_FILTER = Setting.boolSetting(
        "search.aggs.rewrite_to_filter_by_filter",
        true,
        Property.Dynamic,
        Property.NodeScope