The interviewer told she wanted me to start with the UX aspect, buttons, card reader, cash insert, literally every detail including the power strip. Then she said she wanted me to slowly keep getting lower level. So after talking about the UX, she wanted me to talk about the software to handle cards placed in the vending machine. Then talk about the internet being used to verify the card and more. Got down to EE level eventually about motors used to move the drinks/snacks.