You have a pandas script that processes a table of several million rows; it takes half an hour and sometimes runs out of memory. How would you speed it up?
~4 min by voice
How to approach it
They're checking whether the candidate can systematically find the bottleneck in pandas code and knows the typical causes of slowness and memory overuse: row-wise operations, bloated types, unnecessary data and copies. The point is to propose concrete engineering techniques, not "buy a bigger server".
The interviewer will ask this question and listen. Think out loud and ask for a hint if you need one. When you're done, pause or tap “That's my answer”. In about a minute, your score and the points you covered show up here.