They didn’t give you parameter 26837 – I’m just giving you that so you can see an execution plan.
You don’t have to talk me through the query itself, or what you’d want to do to fix it. In fact, I want you to avoid that altogether.
Instead, tell me what things you need to know before you start tuning, and explain how you’re going to get them.
I think, based on the noise in the comments section, that this is a good question. Good interview questions are separating in equilibrium (as opposed to pooling). The question itself is straightforward, but people have such a tendency to jump the gun that they try to answer a question which isn’t being asked. Then, when reading the question, the set of steps and processes people have is interesting because of how much they differ.
Bonus question: take your interview answer (“I would do X and Y and Z and then A and B and C and maybe D.”) and apply it to the last time you had this scenario come up. How many of [A-DX-Z] did you actually do?