I run a solo SaaS product with 15,000+ users. I use the "arcane/wizardry" techniques still. I simply run "make deploy" and a new production build is made and rsync'd to production. Then the script executes a "deploy.sh" on the production server which reloads the system process to pick up the new binary. Poof.
And if your singular production server catches on fire?
I do daily backups and have the ability to deploy a "new" server if need be. It's a little bit of manual work but would be trivial.