Passed the Microsoft Certified: DevOps Engineer Expert (AZ-400) Exam today. Updated the certification page for this certification.
First Expert level exam I've done from Microsoft. Was surprised at how short the exam was: 45 questions (6 on the case study) and 39 multiple choice, no simulations. Took less than an hour from start to finish to take it. Got a 780 on it. Was doing a lot of changing of answers on it on the last pass so no idea whether I was taking the score the right or wrong way.
My main piece of advice is to sit for the AZ-104 (Microsoft Certifed: Azure Administrator Associate) and the AZ-204 (Microsoft Certified: Azure Developer Associate) exams before that. You need to have one of those certs to get the AZ-400 cert, but having both of them really helped me out.