Recruiter reached out to me via LinkedIn. Did an initial phone screen and set up a technical phone interview. The interviewer spent some time going over my background and then switched over to a technical case about how to identify people using multiple devices. Asked me to describe the business value, possible approaches to do it and drilled down into different cases as I built my answer. The interviewer would suggest different paths if he felt I was plateauing. In my opinion, to keep talking about this problem for 45 minutes or so it requires a person to have significant domain knowledge about this problem or have worked in e-commerce previously, since they are looking for specific answers.