One of the main selling points of HotelTonight, the app that allows users to reserve hotel rooms for, yes, that very evening, is its simplicity. In most cities, you just see three hotels, each in a different category — “luxe,” “hip,” and “basic.” Some cities, like Las Vegas and New York, are subdivided into large neighborhoods, and you get three hotels per neighborhood. Today, however, those hotel lists will be expanding, thanks to personalized recommendations.

Co-founder and CEO Sam Shank tells me that on a given day, there are often 20 or 30 hotels competing for those three spots in a given city. At the same time, if you’re making a booking through the app, those three offers may not be ideal for you — for example, they might be in inconvenient locations. So personalization makes sense as a way to show more offers without overwhelming users with a giant list.