How is fastai cnn_learner so fast?

How is fastai cnn_learner so fast?

^^ Someone asked that but removed the question. I am curious too however. How is the fastai cnn resnet so fast with training? Just two epochs of cifar 10 with like a 3 layer resnet on pytorch took me 6 minutes to train on a nvidia titan xp. What does fastai do to train their resnet in literally seconds?