Redis is a key-value store that has evolved beyond its traditional purpose, and clustering allows data to be sharded across multiple nodes. In a cluster, data resides in one place, and each node or shard has a portion of the keyspace, divided into 16,384 slots. Keys are related to slots through hashing functions, which derive a single number from a string of characters. Transactions in Redis only occur within the same hash slot, ensuring high throughput and eliminating failures scenarios. To approach this with advanced planning, hashtags can be used to logically divide keys among nodes, while Redis Enterprise offers regular expressions for sharding. When designing an application for clustering, it's essential to consider command limitations and potential key issues.