All the nodes in a Redis cluster must reside in the same region

While using Redis with cluster mode enabled, asynchronous replication mechanisms are used to keep the read replicas synchronized with the primary. If cluster mode is disabled, the replication mechanism is done synchronously

If you have no replicas and a node fails, you experience no loss of data when using Redis with cluster mode enabled

While using Redis with cluster mode enabled, you cannot manually promote any of the replica nodes to primary

You can scale write capacity for Redis by adding replica nodes