(see KATTA-61 for a related issue) If you add a new node to a katta cluster, it will never be assigned any nodes unless another node goes down. It would be nice to be able to rebalance a cluster by moving shards from the node with the most shards to the node with the least. Rebalancing should, of course, only be done if there is an imbalance worth correcting. My first swag at that rule would be to only rebalance if some node has more than 2 fewer shards than the average number of shards computed by dividing the total number of shards by the number of nodes (using floating point, not integer math). It is also worth having a throttle that limits how often shards are moved. And, of course, it is important that shards not be deleted from where they came from until they are present on the destination node and possibly not even for a while after that.