When conducting an interview, whether at Amazon or any technology company, hiring managers are interested in one of three things - how you can help their organization make money, save money, or save time. The questions they asked will be specific to these objectives. You can prepare for the interview by understanding the organization's mission, the role of the job you are interviewing for, and how you can help them achieve one of these three objectives. In this case, the interviewer is seeking to understand how you can save time.