The live page, the queue depth, the disk, the last successful run. Not a green light from a deploy hook.

Monitoring, alerts, dead-man timers and a morning report, plus incidents written up and fixed for good. This is the layer we run under every product of our own, and the reason a two person studio can operate a portfolio.

Live checks on pages, queues, disks and jobs, with alert thresholds set so the phone stays quiet.
One email a day per system, written for the person accountable, not for an engineer.
Same day write-ups with the permanent fix, so the same thing never pages twice.
Read access to run checks, and deploy access only if we are the ones fixing. Everything is logged and revocable.
The watching, the morning report, alerts, and incident handling with a written fix. Larger changes are scoped separately.
The system does not sleep. Alerts route to whoever is on, and most incidents are caught by a timer before a customer notices.