To be noted: the entire redis content has to fit in memory: Redis is an in-memory but persistent on disk database, so it represents a different trade off where very high write and read speed is achieved with the limitation of data sets that can't be larger than memory.

Persistence https://redis.io/topics/persistence
Modules https://redis.io/modules
Business model https://redislabs.com/try-free/
Licensing shift https://www.theregister.com/2019/02/22/redis_labs_changes_license_funding_60m/

Discussion at Redis as a K/V store for billions of objects