Scenario: Illegal Power Transition - Interview Scenario

Scenario

PMU firmware introduces a new low-power mode that intermittently triggers illegal PST jumps when asynchronous wake and thermal events race.

OBSERVED METRIC
Illegal PST transition count and mode-entry latency spikes under concurrent control stimuli.

45-MINUTE INTERVIEW FLOW
0-5: define context and KPI
5-15: classify first failing LP boundary
15-25: identify proving artifact packet
25-35: propose bounded fix with owner
35-45: define validation matrix and rollback

Common traps to avoid

• Blaming firmware race alone without proving hardware handshake assumptions.

• Checking only nominal mode transitions while skipping stress corners.

• Disabling checks to unblock regressions instead of fixing sequencing contracts.

Scenario debrief

Score response quality on transition-boundary classification, evidence chain, owner assignment, and rollback-safe closure.

intent -> transition behavior -> evidence -> owner action -> closure

escape risk and closure trend

Debrief prompts

1. Which low-power phase boundary failed first and how is it proven?

2. Which failure class best explains the symptom: setup, transition, boundary, retention, or X-prop triage?

3. Which bounded fix and validation matrix close risk with minimal collateral change?

Key takeaways

• Tie each LPV claim to a concrete transition boundary and one proving artifact.

• Prefer minimal reversible fixes with explicit owner and rollback criteria.

Common pitfalls

• Treating power-aware failures as random before boundary classification.

• Waiving X-prop failures before proving impact and root cause.

• Declaring closure without deterministic replay across key modes.