Most projects that you worked on in college and at work already had an established team in place and you were involved in writing features for a very specific component.
So, how do you perform this seemingly absurd task single handedly under an hour?
Understand what the interviewer is asking for.
Draw a box on the (on the white board/laptop screen provided for the interview) that represents the system. Add 5 – 6 major components within this box. Briefly discuss each component to give the interviewer an idea of your thinking process.
So even though your interviewer is not really expecting you to design Google Maps from scratch when you meet him, he wants to understand if you will be a good fit for his team which is working on a similar project. This exercise will give him a good idea of your technical skills.
Don’t pretend to be an expert in an area which is not yours and don’t rush to give an answer. Keeping these small things in mind will help you for your technology interviews.