Currently, you cannot change the partitioning of a stateful service/actor. I'm forced to anticipate future horizontal scale and create that many partitions, so that when nodes are added to the cluster, load is moved off of hot nodes to the new ones.

NoSQL databases, such as MongoDB, rebalance the partitions when adding a node. If I"m doing a range partition and have 5 nodes, the range is sliced up into 5 equal(ish) shards. If I add node later, data is migrated until I have 6 equal(ish) shards.

Having this functionality in Service Fabric for stateful services/actors would allow better horizontal scaling of those services.