There are over 10,000 exercises in Khan Academy. To achieve Proficiency, you must get 100% of the questions correct or get a Familiar skill correct in a quiz, unit test, or course challenge. Achieving Mastery (which is a bigger bonus) doesn't count.

I would think that this badge is possible to earn, but it would take a lot of effort to achieve this difficult task. I also think this badge could be earned multiple times, because Khan Academy constantly updates itself and introduces new exercises, giving you a fresh opportunity to recomplete the task.

What do you think? Is this badge actually possible to earn?