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
}
    }
    private final AtomicInteger dummmyDocIdGenerator = new AtomicInteger();
    
    public static void disableIndexBlock(String index, String block) {
        updateIndexSettings(Settings.builder().put(block, false), index);
    }
    
    public static void enableIndexBlock(String index, String block) {
        if (IndexMetadata.APIBlock.fromSetting(block) == IndexMetadata.APIBlock.READ_ONLY_ALLOW_DELETE || randomBoolean()) {
            
            updateIndexSettings(Settings.builder().put(block, true), index);
        } else {
            indicesAdmin().prepareAddBlock(IndexMetadata.APIBlock.fromSetting(block), index).get();
        }
    }
    
    public static void setClusterReadOnly(boolean value) {
        updateClusterSettings(
            value
                ? Settings.builder().put(Metadata.SETTING_READ_ONLY_SETTING.getKey(), value)
                : Settings.builder().putNull(Metadata.SETTING_READ_ONLY_SETTING.getKey())
        );
    }
    
    public static void updateClusterSettings(Settings.Builder persistentSettings) {
        assertAcked(clusterAdmin().prepareUpdateSettings().setPersistentSettings(persistentSettings).get());
    }
    private static CountDownLatch newLatch(List<CountDownLatch> latches) {
        CountDownLatch l = new CountDownLatch(1);