Duolingo is too ruthless; its first year of revenue was a profit scale of 1 billion dollars, and it actually hasn't monetized much yet. The business model has already been validated. Given its user scale and the stickiness of monthly active users, with a high growth rate of 50%, don’t be misled by the high price-to-earnings ratio; it's somewhat like Amazon's rapid growth after it started making profits, with a steep profit curve.