This was a tough one!
So having already passed AZ-203 earlier in the year and after weeks of trying to cram in a load of study, I managed to pass another online proctored Microsoft Certification this year, AZ-400 Azure DevOps Engineer Expert.
What I will say about this exam is that you definitely need to know more than just Azure and Azure DevOps. You have to have a good understanding DevOps processes, CI/CD pipelines, GitHub and other things like Jenkins, Octopus Deploy, Chef, Puppet, Terraform and YAML to name a few.
Here are the resources that I found useful:
The MS Learn link lays out the prerequisites and skills needed to pass this exam. What I would say, is try and get as much hands on experience as you can. Nothing can beat that. The MS Learn courses do have Sandboxes which is a great feature. And if you don’t have an Azure Subscription, you can get 12 months of free services here.