Just cleared MS-900 with a 91% after about 3 weeks of focused prep, roughly 1.5 hours a day. I had some general IT background but no specific Microsoft 365 administration experience, so I wasn't starting from zero but I also wasn't overconfident going in. Wanted to share what the breakdown actually looked like since the official objective weights are vague.
Cloud concepts and Microsoft 365 core services made up the biggest chunk — probably 35–40% of what I saw. If you don't have a clear mental model of SaaS vs PaaS vs IaaS and where Microsoft 365 fits, that's where to start. Security, compliance, and identity content felt like about 25% of my exam, and I'd underestimated that section in my initial prep, which showed in my early practice scores around 68%.
Microsoft 365 pricing and licensing is genuinely tested and it's annoying to study because the details change. Focus on understanding the logic of license tiers — what's included in Business Basic vs Business Premium vs Enterprise E3 — rather than memorizing every feature point. The exam tests whether you can apply that logic to a scenario, not just recall tier names.
I took MS-900 as my entry point into Microsoft certifications and found the Microsoft Learn paths genuinely useful — more so than third-party material for this particular exam. Free, covers all the objectives, and the practice questions at the end of each module are decent quality.
Three weeks is realistic if you're putting in consistent time. I tried to cram it into 10 days and passed with a 79% but there were sections I felt shaky on. Rushing the cloud fundamentals section specifically is a mistake — it bleeds into every other domain on the exam.
Passed mine in 2.5 weeks with an 87%. Your point about licensing logic is exactly right — I wasted time memorizing specific feature lists when the questions were really testing whether I understood which tier a given business scenario would require. Conceptual understanding over rote memorization.
The security and compliance section surprised me too. Microsoft Purview and Defender products showed up more than I expected from the official objectives. If you're not familiar with what each one does at a high level, it's worth an extra couple of hours there specifically.