The last check before launch

I'm about to launch <one sentence>. Stack: <stack>. Host: <host>.
Here's the project: <paste the file list and key files>

Go through it as if you were a stranger arriving on launch day:
- Error display switched off in production, errors still logged.
- Secrets outside the web root and not in version control.
- HTTPS everywhere, with correct redirects.
- Backups running, and one restored as a test.
- Anything this host does differently from my machine that could bite.
- What happens if 200 people arrive in the same minute.

Rank the findings by how bad they'd be, worst first.