Redis uses asynchronous replication for scalability and data redundancy, allowing multiple slaves to connect to a master and form a graph-like structure. Setting up Redis replication is straightforward, providing flexibility and power. Classic use cases for replication include scaling by allocating resources to databases, ensuring data redundancy at the shard level, and managing persistence. However, sharding addresses read and write scaling challenges more effectively, making access to read-only replicas less necessary in many scenarios. Despite this, certain situations may benefit from having a replica provide read-only database access, such as development purposes.