Right. Almost any time somebody fails an interview it is not because of "very hard questions" but because they did not prepare properly in a sensible manner. People don't want whiteboarding, no programming questions, no mathematical questions, no fermi problems etc. which is plain silly and not realistic. One just needs to know the basics and simple applications of the above which is more than enough to get through most interviews. The key is not to feel overawed/overwhelmed with unknown notations/jargons which is what the actual problem is when people run away from big-O, DS/Algo, Recursion, application of Set Theory/Logic to Programming etc.