Design an incident response and on-call system for a platform with 24/7 uptime requirements run by a team across a single time zone.

Cover: the staffing reality gap (24/7 coverage requirements vs. single-time-zone team) and how that's typically addressed — a rotating on-call schedule with explicit escalation tiers, automated alerting tied to SLO breaches (not infrastructure noise) to minimize unnecessary pages, a clear severity matrix defining what actually warrants waking someone up versus what can wait until business hours, and runbooks detailed enough that an on-call engineer outside their usual area of expertise can still execute a safe initial mitigation before deeper specialist involvement is needed.