Multi Tier Storage
Upstash keeps your data both in memory and disk. This design provides:- Data safety with persistent storage
 - Low latency with in memory access
 - Price flexibility by using memory only for active data
 

Can I use Upstash as a database?
Definitely, yes. Some users are worried that Redis data will be lost when a
server crashes. This is not the case for Upstash thanks to Durable Storage.
Data is reloaded to memory from block storage in case of a server crash.
Moreover, except for the free tier, all paid tier databases provide extra redundancy by replicating data to multiple instances.