Tell Me About the First Real Bug You Fixed in Production Code
Behavioral and LeadershipOwnershipAsked atJuniorMidUpdated
“Tell me about the first real bug you fixed in production code. Walk me through how you tracked it down.”
They're checking whether you debug with evidence. Strong answers reproduce the bug first, find the cause, prove the fix with a test, and confirm it worked for users.
Rubric by Level
Junior
- Reproduced the bug before changing any code.
- Dug in with logs, a debugger, or bisecting, and can explain the cause.
- Wrote a test or a repeatable reproduction that would have caught it.
- Followed the fix through review and confirmed it in production.
Mid
- Checked whether the same bug existed elsewhere and fixed those spots too.
- Sized the impact on users and told the right people.
- Added monitoring or an alert so a regression would show up fast.
Senior
- Fixed the class of bug, like a shared helper or a safer API, along with the instance.
- Led a short write-up so the team understood the cause.
- Weighed a quick patch against a deeper fix and explains the choice.
Principal
- Uses the bug to show a systemic gap, like testing strategy or ownership, and the investment that closed it.
- Explains how you decided the fix was worth the cost across the org.
- Shows the result over time, like fewer incidents of that kind.
Red Flags
- Patched a symptom without understanding why ("I added a null check and it stopped throwing").
- Didn't verify the fix actually shipped and worked for users.
Follow-Ups to Expect
- If the same bug appeared in a different module, would your fix have prevented it there too?
A Story Shape That Holds Up
The Symptom
What users or alerts saw, and how you reproduced it.
The Hunt
The tools you used and the wrong turns you ruled out.
The Fix and the Test
What you changed and the test that proves it.
After It Shipped
How you confirmed it in production, and what you'd check sooner.