SRE Best Practices Practical By Samson Tanimawo, PhD Published Jul 26, 2026 4 min read

The Three-Page Rule for the On-Call Mental Model

The mental model that fits on one page. Three pages, one each for: live state, recent deploys, escalation paths. Why three is the right number.

Page 1: live state

The current state of every service the on-call owns. Latency, error rate, recent alerts. One row per service; status icon.

Updated automatically; the on-call does not maintain it. Any time-decay risk means the page is stale and untrustworthy.

Surfaces incidents in flight without scrolling. Single screen; can be checked while talking to the previous on-call.

Every deploy in the last 4 hours, with service, version, and one-line description. Sorted reverse-chronological.

When an alert fires, page 2 is the first place to look. 'What changed' is the most common cause of new incidents.

Deploys older than 4 hours fall off; the operator can dig deeper if needed but the default surface is recent.

Per-service: who to page for what kind of failure. Database team for DB issues; network team for connectivity; etc.

Includes secondary on-calls, escalation managers, and 'do not disturb' lists.

Single source of truth. If escalation paths live in 4 places, mistakes happen during incidents. Consolidate.