Practice
Tell me about the hardest bug you have tracked down. How did you find the cause?
Read first: a sample answer
Fictional sample answer written by JoRoute to show the shape of a strong answer. Do not copy it: replace every detail with what is true for you.
At a payments startup in 2023, our checkout page crashed for about 5% of customers. Debugging it was my job that week. I reproduced the crash from the logs, bisected the recent releases and found a missing null check on the payment response. I fixed it, added a test and a log alert. Crash reports fell from 40 a day to zero within a week, and I learned to check third-party responses before trusting them.