how they describe what they want to work on and their experience, looking at their personal projects to see if any attention was paid to design, what they do with our take home exercise... it's really not actually hard to sift. most engineers just straight up say they don't have design sensibilities. and you can pretty quickly tell if someone who claims to have design sensibilities has chops for it by just glancing at some of their prior work.
what i found is that there are some people who say they are interested in design but are pretty bad at our technical interview, like totally in a lower rung than the engineering candidates, and very very rarely do you find someone that is a 7/10 or above in both design sensibility and engineering chops, even rarer to find an 8 or a 9. (arbitrary scoring scale for conveying my point -- i don't have a specific rubric for this)
