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
context.fetchFieldsContext(fetchFieldsContext);
        }
        if (source.highlighter() != null) {
            HighlightBuilder highlightBuilder = source.highlighter();
            try {
                context.highlight(highlightBuilder.build(searchExecutionContext));
            } catch (IOException e) {
                throw new SearchException(shardTarget, "failed to create SearchContextHighlighter", e);
            }
        }
        if (source.scriptFields() != null && source.size() != 0) {
            int maxAllowedScriptFields = searchExecutionContext.getIndexSettings().getMaxScriptFields();
            if (source.scriptFields().size() > maxAllowedScriptFields) {
                throw new IllegalArgumentException(
                    "Trying to retrieve too many script_fields. Must be less than or equal to: ["
                        + maxAllowedScriptFields
                        + "] but was ["
                        + source.scriptFields().size()
                        + "]. This limit can be set by changing the ["
                        + IndexSettings.MAX_SCRIPT_FIELDS_SETTING.getKey()
                        + "] index level setting."
                );
            }
            for (org.elasticsearch.search.builder.SearchSourceBuilder.ScriptField field : source.scriptFields()) {
                FieldScript.Factory factory = scriptService.compile(field.script(), FieldScript.CONTEXT);
                SearchLookup lookup = context.getSearchExecutionContext().lookup();
                
                
                FieldScript.LeafFactory searchScript = factory.newFactory(field.script().getParams(), lookup);
                context.scriptFields().add(new ScriptField(field.fieldName(), searchScript, field.ignoreFailure()));