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
}
    }
    protected void ensureClusterStateCanBeReadByNodeTool() throws IOException {
        if (cluster() != null && cluster().size() > 0) {
            final Client masterClient = client();
            Metadata metadata = masterClient.admin().cluster().prepareState().all().get().getState().metadata();
            final Map<String, String> serializationParams = Maps.newMapWithExpectedSize(2);
            serializationParams.put("binary", "true");
            serializationParams.put(Metadata.CONTEXT_MODE_PARAM, Metadata.CONTEXT_MODE_GATEWAY);
            final ToXContent.Params serializationFormatParams = new ToXContent.MapParams(serializationParams);
            
            final Map<String, String> compareParams = Maps.newMapWithExpectedSize(2);
            compareParams.put(Metadata.CONTEXT_MODE_PARAM, Metadata.CONTEXT_MODE_GATEWAY);
            final ToXContent.Params compareFormatParams = new ToXContent.MapParams(compareParams);
            {
                Metadata metadataWithoutIndices = Metadata.builder(metadata).removeAllIndices().build();
                XContentBuilder builder = SmileXContent.contentBuilder();
                builder.startObject();
                ChunkedToXContent.wrapAsToXContent(metadataWithoutIndices).toXContent(builder, serializationFormatParams);
                builder.endObject();
                final BytesReference originalBytes = BytesReference.bytes(builder);
                XContentBuilder compareBuilder = SmileXContent.contentBuilder();
                compareBuilder.startObject();
                ChunkedToXContent.wrapAsToXContent(metadataWithoutIndices).toXContent(compareBuilder, compareFormatParams);
                compareBuilder.endObject();
                final BytesReference compareOriginalBytes = BytesReference.bytes(compareBuilder);
                final Metadata loadedMetadata;
                try (
                    XContentParser parser = createParser(
                        parserConfig().withRegistry(ElasticsearchNodeCommand.namedXContentRegistry),