A load test showed that at 500 requests per second, response time grew from 200 milliseconds to three seconds. How would you track down the cause, and what would you put in the report?
~4 min by voice
How to approach it
This checks whether the candidate can systematically find a bottleneck under load rather than just noting 'it's slow'. Interviewers look at how they validate the test itself, read the metrics, go through the layers of the system (resources, database, dependencies) and frame the conclusion relative to the SLA.
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.