Redis is a fast, open-source, in-memory key-value data store that is commonly used as a cache to store frequently accessed data in memory so that applications can be responsive to users. It delivers sub-millisecond response times enabling millions of requests per second for applications.
It is also used as a Pub/Sub messaging solution, allowing messages to be passed to channels and for all subscribers to that channel to receive that message. This feature enables information to flow quickly through the platform without using up space in the database as messages are not stored.
Redis offers a primary-replica architecture in a single node primary or a clustered topology. This allows you to build highly available solutions providing consistent performance and reliability. Scaling the cluster size up or down is done very easily, this allows the cluster to adjust to any demands.