Obviously these are application decisions.

You, obviously, don't commit important data only to a session that you can loose, if the application does not allow it.

We use redis as infrastructure. To route events and as a cache.

For us redis could go down and we would merely see a degradation of our service with no data loss.

I recommend using redis like that. And then use a database that supports transactions for real data problems.

But we are different. And that's OK.

If you consider it important, you have to store it in a real database. No buts. If you don't consider it important, sharded redis works fine.