STAR is for behavioural and operational questions: "Tell me about a time when..." or "Walk me through a recent incident..."
S — Situation: The context. What was happening, what was the environment. T — Task: What you specifically needed to do, what was your responsibility. A — Action: What you actually did, in concrete detail. Use "I" not "we." R — Result: The outcome, ideally with a number. Plus what you learned or what changed.
For ops/SRE roles, always add a fifth element: Preventative action / runbook update. Hiring managers love this because it shows you don't just fix, you prevent recurrence.