Note that Redis only provides best effort consistency: it means that sometimes it can lose acknowledged data in special conditions (during failovers, or during restarts with a relaxed fsync policy). So it will never pass Jepsen tests in the default setup, but may pass it only when Redis is used with a linerizable algorithm on top of it that uses Redis as a state machine for a consensus protocol. But this does not mean that people haven't applied Redis for data storage with success. For instance many *SQL failover solutions, also can't pass Jepsen tests, yet people use them to store real world data. There are a lot of applications where to be able to really scale well and with a low cost (spinning sometimes 1/10 or 1/100 of nodes) makes perfectly viable to pick a system that is designed for that, and as a price, will lose a window of acknowledged writes during failures, while trying hard to avoid it in common failure scenarios.