Booking.com runs more than 1,000 rigorous tests simultaneously and, by my estimates, more than 25,000 tests a year. At any given time, quadrillions (millions of billions) of landing-page permutations are live, meaning two customers in the same location are unlikely to see the same version. All this experimentation has helped transform the company from a small Dutch start-up to the world’s largest online accommodation platform in less than two decades.

Read more: https://hbr.org/2020/03/building-a-culture-of-experimentation