Current development has been focused on improving the flexibility of secondary indexes. There was some funky stuff achieved by some users using overloaded 2i terms and distributed processing of regular expressions against those terms - the aim is now to make this more flexible to the modern developer using the language of projected attributes and filter expressions (ala DynamoDB). There's also some active work to both replicate-to and full-sync (i.e. reconcile with) external OpenSearch clusters.
The primary goal for OpenRiak is stability under load/failure as a K/V store - so the ultra-flexibility of in-built SOLR querying has been sacrificed in the move towards that aim. Anything that can do harm is to be offloaded or constrained.