Comment by webmonkeyuk

I suspect:

- memcached if you don't need to persist the data

- Redis if you don't know whether you need to use Redis or FoundationDB

- FoundationDB if you learn that Redis doesn't do what you need

I don't mean this in any kind of a derogatory way but I suspect that if you need to ask then you probably don't need FDB.

The principle of keeping tech stacks boring and using well established components is less exciting as an Engineer but is usually the best choice.