This isn't just an indexing question. You'll be asked to describe how to distribute amongst multiple data centers, or you'll be asked how to determine which widgets to serve (stock price, YouTube video, image search), or you'll be asked how to built how a system for data processing. Just do your best and correct mistakes as you make them. Google search was't built in a day by a single person, and you certainly won't build it in the 45 minutes you have.