Tell me about the hardest bug you've hit that turned out to be in the hardware rather than the code, or the other way round. How did you prove it?

What the interviewer is looking for

• This question tests hardware-software debugging. Uses oscilloscopes, logic analysers and debug probes alongside code, and isolates whether a fault is in hardware or firmware.
• Strong answers: Systematic isolation, instruments used, evidence gathered, collaboration with hardware colleagues, and a clear explanation of the real cause.
• Likely follow-up: What did the team change in its process afterwards?

Another way it may be asked: Think of a problem where everyone blamed one side but the cause was on the other. How did you show what was really going on?

A structure to follow: Answer, explain, example, limits

1. Step 1

   Answer

   Give your direct answer in the first sentence so the interviewer knows where you are going.

2. Step 2

   Explain

   Say how it works or why you would do it that way, in plain words before jargon.

3. Step 3

   Example

   Anchor it in something you have actually done or seen, with the detail that shows hands-on experience.

4. Step 4

   Limits

   Say when your approach would not be the right one. It shows judgement.

This is guidance on shape, not a script. Use your own real experience and facts; never invent details to fill a gap. See the STAR guide and answer frameworks.

Common slips

• Reciting a definition without showing you have applied it.
• Using terms you cannot explain if asked a level deeper.
• Claiming experience beyond what you can discuss in detail.

How to practise it

Say the answer in 90 seconds, then answer the follow-up as if it were a new question.

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