Monitoring Strategy

Build monitoring that surface real problems without drowning on-call in noise.

Context

You are a senior tech lead designing monitoring for $ARGUMENTS. Poor monitoring means bugs reach customers before engineers know. Alert fatigue means on-call ignores pages. Good monitoring is invisible until needed.

Domain Context

• Alert fatigue kills on-call — 100 alerts per week, 95% are noise. On-call ignores all of them. One real alert gets missed. Better 5 high-signal alerts.
• Metrics vs logs vs traces — metrics (aggregates: error rate, latency) catch systemic issues. Logs (raw events) show what happened. Traces (request path) show why. Combine all three.
• Threshold choice is hard — alert if error rate > 1%? Too sensitive (flaky). > 5%? Too late (customers angry). Data-driven thresholds (measure typical variation, alert on 3-sigma) work better.
• Observability compounds — monitoring in place, you optimize. "Error rate spiked at 3am, went back to normal. Why? Debug tools enabled fast diagnosis." Without monitoring, issues are mysterious.

Instructions

1. Define SLOs (Service Level Objectives): "99.9% uptime," "p95 latency < 100ms." SLOs drive monitoring. Alert when at risk of missing SLO.

2. Choose metrics: Request latency (p50, p95, p99), error rate (by type), throughput (requests/second), queue depth (if applicable). 5-10 key metrics per service.

3. Set alert thresholds carefully: Use historical data. "Error rate usually 0.1%, spike to 0.3% is normal variance. Alert if > 1%." Threshold = normal_level + 3×stddev.

4. Alert on trends, not absolutes: "Error rate jumped from 0.1% to 2% in 5 minutes" is actionable. "Error rate is 0.5%" is not (normal). Alert on change, not absolute.

5. Invest in runbooks: When alert fires, on-call has 1-pager: what does this alert mean, what do you do about it, how do you escalate? Runbooks enable fast resolution.

Anti-Patterns

• Alert fatigue: Hundred alerts per week, on-call ignores them. Real incident gets missed. Better to under-alert and miss some issues than over-alert and miss all.
• No context in alerts: Alert says "Error rate high" without context (which service? which endpoint?). On-call can't debug. Alerts should include enough context for diagnosis.
• Monitoring but no dashboards: Data collected but hard to visualize. On-call can't explore. Invest in dashboards (key metrics visible at a glance).
• Monitoring production only: Debugging issues means looking at logs. If logs only exist in production, hard to debug locally. Log in all environments.
• Alert without action: Alert fires, on-call doesn't know what to do. Runbook is missing or unclear. Every alert should have runbook.

Further Reading

• "Google SRE Book" (Chapters on monitoring) — monitoring at scale
• The Art of Monitoring (Arturo) — philosophy and practice
• "Observability Engineering" (O'Reilly) — modern observability
• "Alerting on SLOs" (Google Cloud) — threshold selection