Debugging approach
Part of the Backend Developer Roadmap
In short
"How do you debug a production issue?" tests your process, not your luck. Interviewers want a calm, step-by-step method backed by evidence.
Interviewers often ask how you approach a bug you've never seen before — they're evaluating your process, not just whether you 'know' the answer.
Think of it like this
A good doctor's checkup
A good doctor doesn't prescribe medicine the moment you walk in. She asks about symptoms, checks your temperature, orders a test if needed, then treats the cause and tells you how to avoid it next time.
Watch it happen
Answering "how do you debug?"
1/6"First I reproduce it: which endpoint, which users, since when. A bug I can trigger is half solved."
The big ideas
What you need to know
Reproduce first
Find exact steps or the exact request. Without a reproduction, you can't prove a fix.
What changed?
Deploys, config, traffic and dependencies. Most incidents follow a change, so check the timeline early.
Divide and conquer
Narrow it down by halves: client or server, which service, which function. git bisect does this for commits.
Write it down
A short post-incident note with cause, fix and prevention shows maturity in interviews and at work.
Save yourself the pain
Common mistakes
Oops
Answering "I add console.logs everywhere until I find it."
Do this instead
Logs are fine, but describe a method: reproduce, narrow down, test one hypothesis at a time.
Oops
Changing several things at once and redeploying.
Do this instead
Change one thing, then verify. Otherwise you never know what actually fixed it.
Your mission
Tell a real bug story
Quick check
Errors jumped right after this afternoon's deploy. What's the best first step?
Go deeper
- 1Prepare a real story: a tricky bug you found and how you systematically tracked it down.
- 2Practice narrating your debugging process out loud during mock problems.
- 3Structure your answer: reproduce, isolate, hypothesize, verify, fix.
More behavioral at this stop
Explain your projects
Team collaboration
Code review experience
Trade-off discussions
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