This is the second exam if you want to achieve the Azure Solutions Architect Expert certification. I already explained my thoughts about the AZ-303 here.
In my opinion AZ-304 is harder than the AZ-303 primarily because you need to learn many details and limitations of many Azure services. Even if you worked many years with Azure you still might easily fail it just because you worked only with some subset of features that you needed for the everyday work.
The areas of knowledge are similar to the other Azure solution architect exams: storage services, networking, data transformation, identity management, security, resilience and backups. For me the most confusing part was the identity management – unless you really worked a lot with Active Directory it’s pretty hard to figure out the solutions to the questions.
That is also the part that’s least covered by the preparation courses. The Cloudacademy Exam Preparation Path this time was only covering the basics, and it might help you answer about 30% of the questions. For the rest you need to practice or search for different learning materials.
Overall thought – pass it only if you worked with different Azure services and want to ensure that your knowledge is still actual or to check for best practices. Makes no sense passing if you only begin working with Azure – you will just be memorizing lots of stuff you don’t understand. Pass the AZ-900 instead.
P.S. A bit of afterthoughts – I spent about 40 hours to prepare for it with only basic knowledge and some practice on real Azure environments. And now I’m not sure what’s supposed to be your career choice if you pass it – besides Microsoft Consultant or “A Trainer, who prepares for AZ-304 exam” that is. My point is – to be able to really architect Azure solutions you’ll need to spend much more time and likely a thousand bucks on Azure services to play around with them and test their limits.