Amazon ElastiCache for Redis introduces Online Cluster Resizing to add and remove shards from a running cluster. You can now dynamically scale-out or scale-in your Redis cluster workloads to adapt to changes in demand. ElastiCache will resize the cluster and redistribute hash slots uniformly across the new shard configuration, all while the cluster continues to stay online and serve requests. Additionally, for optimized processing, you can also rebalance a cluster and uniformly distribute the slot space, without changing the number of shards.