Clarify scope & goals- Goal: quantify user/business impact from the 12-month undetected degradation, find why it was missed, prioritize fixes, and produce a leadership-ready report that states uncertainty and recommended mitigations.- Stakeholders: product owner, security, data/analytics, observability, infra, finance. Set 2-week cadence for investigation sprints.1) Data collection & baseline reconstruction- Inventory: list services, ingress points, SLOs, SLIs, dashboards, alerts, logging retention, APM traces, deploy history and config changes for last 18 months.- Rehydrate lost telemetry (if sampled): pull raw logs/traces from backups, backups of metrics, CDN/edge logs, billing/CS ticket history.- Example queries:promql
sum(rate(http_requests_total{job="api"}[30d])) by (status)
sql
SELECT date_trunc('day', ts) as day, count(*) as errors FROM support_tickets WHERE created_at >= '2024-01-01' GROUP BY day;
2) Quantify impact- Define metrics: user-facing error rate, latency P95/P99, throughput, revenue-related metrics (checkout conversion), capacity costs.- Reconstruct time series, compute delta vs healthy baseline (use prior year or sibling services). Report cumulative lost revenue, increased cost, MTTR regressions, and customer impacts (# incidents, SLA breaches).- Use counterfactuals: simulate “if monitored” trend using early-detection thresholds to estimate how many incidents/transactions would have been prevented.3) Root-cause & instrumentation gap analysis- Map missing observability: missing SLI coverage, poor cardinality, low retention, no synthetic checks, missing end-to-end traces, alert thresholds/inhibition issues.- Trace chain: code/deploy/date correlation -> config drift -> resource exhaustion -> slow leak. Document evidence and confidence level per link (high/medium/low).4) Prioritize fixes (risk x effort)- Critical (P0): add SLIs for user journeys, end-to-end synthetic tests, increase metric retention for critical metrics, add tracing for high-latency paths.- Medium: refine alerting (SLO-based alerts), add burn-rate policies, dashboard templates.- Low: dashboard cosmetic, historical clean-up.- Provide implementation estimate (dev hours), expected reduction in detection time, and residual risks.5) Report for leadership- Executive summary: one-paragraph impact (quantified numbers + uncertainty range).- Timeline visual: when degradation began, detection gap, key events.- Findings: bullet list of root causes and instrumentation shortfalls with confidence bands.- Recommendations: prioritized roadmap with costs and expected KPIs improvement.- Uncertainty & assumptions: describe missing data, confidence intervals, key assumptions for counterfactuals.- Ask: sign-off for immediate P0 fixes and budget for audits/retention.6) Governance & follow-up- Deliverables: remediation tickets, updated SLOs, quarterly observability review, runbook updates, postmortem with blameless language.- Measure success: monitor time-to-detect, time-to-resolve, SLO burn-rate over next 90 days.This approach balances evidence-based quantification, practical remediation prioritized by risk/effort, and a transparent leadership report that communicates both impact and uncertainty.