I don’t like keeping my users in the dark, no matter how “untechnical” they are; it makes me feel like I don’t respect them enough to understand, even at a high level, what’s going on. In your case, usually I’d say something like “We’re having issues with our database right now; please try refreshing or going to the home page. If this happens again, you can contact support at support@”. So they have a general idea of what went wrong, which they can mention when contacting support (if I get a bunch of these, maybe the database migration isn’t going well?) and they don’t feel like I’m treating them like a child. More technical users can try to stay away from operations that will touch the database, or optionally take a look at the logs that I hide behind a “details” button.