nw-investigation-techniques

Investigation Techniques

Problem Categorization

Technical Problems

| Category | Sub-Category | Common Symptoms |

|----------|-------------|-----------------|

| System Failures | App crashes, memory leaks, deadlocks, data corruption | Service unavailability, resource exhaustion, integrity errors |

| System Failures | Hardware, network, database, security | Connectivity loss, capacity limits, access failures |

| Performance | Response time: slow queries, latency, algorithmic inefficiency | High p95/p99, user-reported slowness |

| Performance | Throughput: thread pool exhaustion, connection limits, queue backlog | Reduced capacity, growing queues |

| Integration | Internal: component comms, data format, version conflicts | Interface errors, serialization failures |

| Integration | External: third-party availability, API changes, auth failures | Timeouts, contract violations |

Operational Problems

| Category | Common Symptoms |

|----------|-----------------|

| Deployment: script failures, config drift, migration errors | Failed releases, environment inconsistencies |

| Monitoring: alerting gaps, backup failures, incident response | Missed incidents, slow recovery |

| Human factors: communication gaps, knowledge silos, skill gaps | Repeated mistakes, slow onboarding |

Evidence Collection

Technical Evidence Sources

Logs: application (timestamp correlation) | system/infrastructure | database | network traces

Metrics: performance/resource utilization | error rates/response time trends | user behavior/transaction patterns | infrastructure health/capacity

Configuration: system/deployment settings | code changes/VCS history (git log, blame) | env vars/dependencies | security/access controls

Evidence Validation

1. Cross-reference: verify from multiple independent sources
2. Timestamp validation: confirm event sequence accuracy
3. Completeness check: identify data gaps/corruption
4. Correlation vs causation: distinguish co-occurrence from causation

Analysis Techniques

Quantitative

• Trend: time series of metrics, error pattern frequency
• Distribution: response time percentiles, error rate across components
• Pattern recognition: log anomalies, behavior patterns, error clustering

Qualitative

• Timeline reconstruction: detailed incident timeline, correlate changes with symptoms
• Process analysis: workflow disruptions, communication flow, decision chains
• Environmental: recent changes, system load, external factors, related incidents

Solution Design Patterns

Immediate Mitigations (restore service)

Quick fixes | workarounds to minimize impact | emergency procedures | monitoring enhancements

Permanent Fixes (prevent recurrence)

Architecture modifications | code quality/defensive programming | config management/environment consistency | testing/validation improvements

Early Detection (catch faster)

Leading indicators | anomaly detection/predictive alerting | automated quality gates | threshold tuning from learnings

Solution Prioritization Matrix

| Priority | Criteria | Action |

|----------|----------|--------|

| P0 | Active incident, users impacted | Immediate mitigation, hours |

| P1 | Root cause fix for recurring issue | Permanent fix, current sprint |

| P2 | Prevention for potential issues | Next sprint |

| P3 | Systemic improvement | Backlog with evidence |