The On-Call Rotation Rule of Six

Six engineers minimum. Below six, the rotation is unsustainable. The math, the symptoms of an under-staffed rotation, and the path back.

The math

5-person rotation: each person is on-call 1 in 5 weeks. 10 weekends a year; 70 weeknights.

6-person rotation: 1 in 6 weeks. 8 weekends; 56 weeknights. Materially different.

Below 5: people quit. The rotation collapses.

Under-staffed symptoms

Burnout. People showing up tired even on non-on-call weeks; sleep debt.

Quitting. The on-call rotation is the proximate cause for most SRE departures.

Quality drops. Tired on-calls miss things; incidents take longer.

Path back to six

Hire. The most direct path; takes 3-6 months to onboard.

Cross-train product engineers to participate. Adds capacity faster; quality is mixed but better than under-staffed.

Outsource non-critical hours. Vendor on-call for nights; in-house for business hours. Imperfect but maintainable.