A query that used to run in milliseconds now takes seconds after the table grew to tens of millions of rows. How would you investigate, and what can you do about it?
~4 min by voice
How to approach it
This checks whether the candidate can systematically diagnose a slow query from its execution plan instead of guessing: find the cause (no index, index not used, stale statistics), design the index correctly and apply changes safely in production while accounting for their cost.
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.