I just passed the GCE ACE exam one hour ago. It was quite a bit more difficult than I had expected.
I have been using GCP for 2 years. All of my experience was in GCE, Load Balancers, GCS, Cloud SQL, Datastore and Cloud Functions.
I took Mattias’s course and it was great to get my feet wet. Going through the material a second time helped and doing the practice exam many times solidified some information. The kubernetes deep dive by Nigel was good as well. It helped me understand kubernetes much better. I also took Google Kubernetes Engine (GKE): Beginner to Pro by Tim Berry which I found very useful. I found that course to be easier to understand or maybe I just needed to hear the same things again. I also got the Associate Cloud Engineer Study Guide by Dan Sullivan and practiced using those tests and online exams many times.
The above studying took just under 4 months. It probably would have better to compress the studying into 2 months but I was doing this during whatever spare time I have.
As for the exam, my advice is to feel comfortable with each and every service and how they integrate with each other. I had many questions that had to do with that. One example was connecting Spanner with Bigtable and GCS.
In almost all cases, they’re looking for the most cost efficient solution and Google Recommendations must be factored in.
My exam consisted of few Kubernetes questions (maybe 3 total).
The majority of the questions were related to making services work across projects or from on-prem to GCP. You need to know security inside and out. I had a handful of questions that had to do with VPN.
Billing and logging questions were also scattered in there, but you absolutely need to remember permissions as they will come in handy.
I hope this helps someone.
Good luck all!