It is possible you are referring to one of the following:
(Hypothetical: 3.8/5 – based on common issues with "hardest" prep materials) the hardest interview2 top
Securing a position at a top-tier firm often involves a gauntlet of rounds that test not just skill, but sheer mental endurance. Organizations like and Google are consistently rated as having some of the world's most difficult interview processes. The Gauntlet: A Story of the "Hardest" Interview It is possible you are referring to one