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
test/framework/src/main/java/org/elasticsearch/test/ESIntegTestCase.java
mockPlugins,
            getClientWrapper(),
            forbidPrivateIndexSettings(),
            forceSingleDataPath(),
            autoManageVotingExclusions()
        );
    }
    private NodeConfigurationSource getNodeConfigSource() {
        Settings.Builder initialNodeSettings = Settings.builder();
        if (addMockTransportService()) {
            initialNodeSettings.put(NetworkModule.TRANSPORT_TYPE_KEY, getTestTransportType());
        }
        boolean enableConcurrentSearch = enableConcurrentSearch();
        if (enableConcurrentSearch) {
            initialNodeSettings.put(SearchService.QUERY_PHASE_PARALLEL_COLLECTION_ENABLED.getKey(), true);
            initialNodeSettings.put(SearchService.MINIMUM_DOCS_PER_SLICE.getKey(), 1);
        }
        return new NodeConfigurationSource() {
            @Override
            public Settings nodeSettings(int nodeOrdinal, Settings otherSettings) {
                return Settings.builder()
                    .put(initialNodeSettings.build())
                    .put(ESIntegTestCase.this.nodeSettings(nodeOrdinal, otherSettings))
                    .build();
            }
            @Override
            public Path nodeConfigPath(int nodeOrdinal) {
                return ESIntegTestCase.this.nodeConfigPath(nodeOrdinal);
            }
            @Override