Scaling up business culture without bureaucratizing it is one of the biggest challenges of any founder, and Airbnb found the answer by redesigning its HR as if it were a product: the Mark Levy method. When Mark Levy arrived at Airbnb in 2013, the company had already passed through Y Combinator and faced explosive growth. One of the founders issued a clear warning: don’t ruin culture as we scale. The familiar version of that phrase summarized the…