So far I’ve passed Basic Chef Fluency, and Local Cookbook Development (parts 1 & 2). One more badge to go .. I’m going to do Deploying Cookbooks next, it looks like a far easier option than Extending Chef. You have to complete three badges in order to become a Chef Certified Developer.
The material is fairly easy for me, I’ve been working with Chef configuration software since 2012, and have trained with Chef Software, Inc. to be a trainer for their Fundamentals (now called Essentials) training course. But, like with the AWS exams, things are constantly changing, so you have to keep on top of your game.