Recipe

5-whys facilitation guide

A structured method to trace any problem back to its root cause through five layers of inquiry.

When to use it

  • A production incident just closed and you need a blameless postmortem.
  • A recurring bug keeps slipping through code review.
  • Team velocity dropped and the surface reason doesn't explain it.
  • Customer churn spiked in one cohort — you want the systemic driver.

The core rule

Ask “why” five times. Each answer becomes the premise for the next question. Stop when you reach a process gap or a missing safeguard — never stop at human error.

Facilitation script

  1. Frame the problem.
    Write a one-sentence statement everyone agrees on. Example: “Checkout latency exceeded 4s for EU users on Tuesday.”
  2. Why #1.
    “Why did checkout latency exceed 4s?” — record the answer verbatim.
  3. Why #2–#4.
    Chain each answer into the next why. Resist the urge to jump to a solution. Stay in inquiry.
  4. Why #5.
    The fifth answer should surface a process gap. If it still points to a person, ask one more why.
  5. Capture the countermeasure.
    Write a single action item that prevents the root cause from recurring. Assign an owner and a deadline.

Real example

Problem: DB connection pool exhausted in prod.

  1. 1. Why? — Connection count hit the 200 limit.
  2. 2. Why? — A background job opened 180 connections in a tight loop.
  3. 3. Why? — The job didn't reuse the pool; it created raw connections.
  4. 4. Why? — The migration from pg-pool was marked complete but the old code path remained.
  5. 5. Why? — No lint rule or CI check enforced the deprecation.

Countermeasure: Add a CI lint rule blocking raw pg.Client imports.

Anti-patterns

  • Stopping at “the engineer forgot.” That is never the root cause.
  • Asking why six times when five is enough — you’ll drift into philosophy.
  • Running the exercise solo on a complex incident. Bring at least two perspectives.
  • Skipping the written countermeasure. Insight without action is entertainment.

Part of the Meridian engineering playbook. Pair with the incident review template for a complete postmortem workflow.