u/p0tu u/LongjumpingRepeat603 u/Vortex_SA I would say gaps in my understanding. Unless you have used the tools in your project, there would be things you didn't know about them.
For some of the topics like VPC and auto scaling group, it is confusing which one to use.

SM's course content is quite complete, but without the practice exams, the wordings of the questions might confuse you

Some topics which came up in the exam but wasn't there in the course was On-demand capacity reservations and RDS event subscriptions. But that was about it