Production Implementation and Runtime Architecture

Core Concept
Guardrail systems run continuously during experiments, computing metrics, comparing against thresholds, and triggering alerts or automatic actions when breached.
Real-Time Pipeline
Stream events (page loads, errors, transactions) to a real-time processor. Aggregate by experiment variant every 5-15 minutes. Compare treatment vs control for each guardrail. Alert or auto-rollback when threshold exceeded with sufficient confidence.
Architecture: event stream → aggregation (5min windows) → statistical comparison → threshold check → action (alert/pause/rollback). Latency from event to action should be <30 minutes for Tier 1 guardrails.
Statistical Considerations
Multiple comparisons problem: checking 10 guardrails every hour for 7 days = 1680 tests. At 5% alpha, expect 84 false positives. Apply corrections: Bonferroni (divide alpha by test count) or sequential testing methods that control family-wise error rate.
💡 Key Insight: Use one-sided tests for guardrails (only care about degradation, not improvement). This increases power to detect harm compared to two-sided tests.
Automated Response
Tier 1 violations trigger automatic rollback: kill switch that moves 100% traffic to control. Tier 2 pauses the experiment (stops new assignments) and alerts on-call. Both require minimal human intervention for safety.

💡 Key Takeaways

✓Pipeline: event stream → 5min aggregation → statistical comparison → threshold check → action

✓Latency from event to action should be <30 minutes for Tier 1 guardrails

✓Multiple comparisons correction needed: 10 guardrails × 168 hours = 1680 tests, 84 false positives at 5% alpha

✓Use one-sided tests for guardrails (only care about degradation) to increase power

📌 Interview Tips

1When explaining pipeline: describe 5-min windows, statistical comparison, auto-rollback within 30min

2For multiple testing: explain Bonferroni correction or sequential methods to control family-wise error

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