Where this falls down is when you're hiring someone who has 10 or 15 years of experience and has forgotten more about day-to-day product development than the fr

Where this falls down is when you're hiring someone who has 10 or 15 years of experience and has forgotten more about day-to-day product development than the freshers have learned about algorithms. So you're asking that guy questions that the freshers have fresh in their minds because it's all they know, and it's totally unsurprising that he fails because he hasn't ever used that knowledge in a work setting. You do need to tailor your interviews to the person's experience level. If you're hiring for experience, ask that person about process and about team forming and about mentoring and leadership. You don't have to be able to write a perfect algorithm as a senior, only to help your juniors over the hurdles keeping them from doing it themselves.