Hacker News Reader

I think the "client" here is the application server, not the web browser.

Then where's the point in this?

Your [pretty long] passphrase can be your key. Or you can take your key file with you.

Having the key derived from your password is also possible, but I think not really that secure.

SpiderOak and Mega deal with this problem as they have e2e encrypted file storage

So that someone getting access to your database's data storage doesn't compromise your data.