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Do not rebuild this — but check the arithmetic, because "paying nothing while idle" is often more expensive than paying something.

Scale-to-zero sounds like free. In practice a small always-on machine costs a few euros a month, has no cold start, and handles far more than most people expect. Idle billing wins for genuinely occasional workloads and loses for anything with steady traffic.

WHEN TO KEEP PAYING
- Preview environments per branch, spun up and destroyed. That is the feature worth the money
- Genuinely spiky or occasional workloads
- A team that wants to deploy without learning a server

WHEN TO SELF-HOST
- One application with steady traffic. Then a VPS with a deploy script does the job for less, and the shape is under Heroku and Fly.io elsewhere in this catalogue

WHAT REPLACES IT, BRIEFLY
- A release directory per deploy, a symlink to the current one, and shared state — the database, uploads, .env — outside the releases and symlinked in
- Deploy: fetch, build, migrate, switch the symlink, restart, health check. A failure at any step leaves the old release serving. Rollback is moving the symlink back, in one command, tested before it is needed
- Caddy for automatic TLS, two lines
- Zero-downtime as a second process on a second port with Caddy switching once the new one answers its health check
- Preview environments as a script deploying a branch to a subdomain with its own database, destroyed when the branch goes. That is the one feature worth reproducing

THE OPERATIONAL FLOOR YOU TAKE ON
Log rotation before the disk fills, a swap file, unattended security updates, a firewall, ssh on keys, certificate renewal monitored, and a disk alert at eighty per cent. Everything on that list fails at once when the disk is full.

AND THE ONE THING NOT TO SELF-HOST
An uptime check from somewhere that is not your machine. Whatever else you run, that stays external.

THE ONE-LINE VERSION
Price a small always-on box against your idle billing. If the traffic is steady, self-hosting wins — and the preview environments are the part worth copying.