Cassandra was literally designed for this class of problem, and redis wasn't, isn't, and never will be. The bucketing they're doing is within a partition - the

Cassandra was literally designed for this class of problem, and redis wasn't, isn't, and never will be. The bucketing they're doing is within a partition - they still get all data in a logical cluster, which gives them transparent linear scalability by adding nodes without having to reshard, and they get fault tolerance/HA, reasonable fsync behavior, and even cross-wan replication - things you'd never get with redis.