Im co-author of Searchkit (www.searchkit.co). This Hierarchical filtering demo uses Elasticsearch aggregations on nested documents with our Hierarchical filter component.

For more info see http://docs.searchkit.co/stable/docs/components/navigation/h...

and

https://www.elastic.co/guide/en/elasticsearch/reference/curr...

Related: https://news.ycombinator.com/item?id=10832207