Recipe

Fishbone (Ishikawa) RCA

Map cause-and-effect chains visually to isolate root causes of incidents, regressions, or outages.

When to use

  • Post-incident reviews with multiple contributing factors
  • Recurring bugs where the fix keeps missing the mark
  • Cross-team incidents spanning infra, code, and process

The 6 M's

Draw a horizontal arrow pointing to the problem statement. Branch six ribs off the spine:

Manpower
Methods
Machines
Materials
Measurements
Mother Nature

Steps

  1. Define the effect. Write the exact symptom at the head of the fish.
  2. Brainstorm causes. For each M, ask “why?” and attach smaller bones.
  3. Drill deeper. Repeat “why?” until you hit actionable root causes.
  4. Validate. Cross-reference with logs, metrics, or timeline data.
  5. Prioritize. Circle the 2-3 bones most likely to prevent recurrence.

Anti-patterns

  • Stopping at “human error” without asking why the system allowed it
  • Filling every M category when only two are relevant
  • Skipping validation and treating the diagram as the conclusion

Pro tip: Run a fishbone session within 24 hours of an incident while memories are fresh. Use a shared whiteboard and timebox brainstorming to 30 minutes.

← Back to docs