Recommendation systems power what we watch, buy, read, and listen to. They work well when there is enough history-past clicks, ratings, purchases, watch time, or searches-to learn patterns. The challenge begins when that history does not exist. This is known as the cold start problem: the difficulty of making good recommendations for a brand-new user (or sometimes a brand-new item) with little to no interaction data.Understanding cold start is important for anyone building data-driven products,…