Zero‑downtime deploys in Magento: a realistic checklist

Minimum checklist:
- `setup:di:compile` outside production.
- `setup:static-content:deploy` in build.
- Atomic symlink switch.
- Cache warmup post‑deploy.

Atomic step example:
```
ln -sfn /var/www/releases/2026_01_31 /var/www/current
```

If you do this wrong, checkout breaks first.

Extra:
- Clear cache only after the symlink swap.
- Validate `env.php` permissions.
- Use health checks for fast rollback.

The difference between “successful deploy” and “incident” is usually two minutes of warmup.