It took me about 10 minutes to generate that writeup the old fashioned 100% organic way, because one of the things that's unspecified is whether you're allowed to use AI to help solve it! So I assumed as it's a job interview question you're not allowed, but now I see other comments saying it was allowed. That would let you get much further.

I think I'd be able to make some progress optimizing this program in two hours but probably not much. I'm not a performance engineer but have designed exotic emulated CPU architectures before, so that helps a lot.