Now we move onto the harder exams. AZ-300 is them first exam you will need if you are working towards Microsoft Certified: Azure Solutions Architect Expert, which I am.
Again this post will develope as I get through it but this video is where I am starting
https://www.youtube.com/watch?v=PrZijM3PRDw
The last exam (AZ-900) caught me off guard a little. Not because it was particulally hard, because I would say it is actually quite an easy exam, but more to do with the format of the questions etc. This guy does a good job of explaining this.