If you have reasonably good knowledge in AWS and whitepapers/videos are like lullabies to you then this might be worth trying. Also if you like to learn by problem solving, then attempting loads of sample questions and then reviewing corresponding study materials in depth might help. But before I delve into it, let me tell you how I ended there.

I started my professional certificate by dutifully doing the certification course in acloudguru.com. In my opinion it is good refresher course if your last certification was quite a while ago. But it not enough to master the complexity of the professional level exam. After reading some of the recommended whitepapers and watching youtube videos, I gave my practise test which I failed. It was a big wakeup call for me.

First problem was I couldn’t complete the practice exam. Just reading the questions and the multiple choice answers was exhausting. As someone for whom English is not first language this is really hard. This is true for the actual exams too. You may come across questions where you not sure you fully understood the nuances. So please keep that in mind (Tip: You are offered additional 30 mins if your first language is not English. Worth utilising it!).

Second problem was I was concentrating on how I would solve the problem rather then pick the best answer from the lot. Sometime no answer is best. You have to choose the best among the given answers.

Third and most important problem was while I had good understand of the concept, it is the nitty gritty, subtleties and how different services work together that count in professional exam. In real life, I would have quickly looked up the appropriate area, asked more questions and decide on the best course of action. However when you read linearly whitepapers/docs/videos, you tend to miss out details if you already have certain familiarity and understanding in that area.

 Here acloudguru discussion forums are really useful. Each question in the AWS practise test has been discussed at length. Used that to review the relevant areas, whitepapers and videos.

 Also AWS conducts a one day virtual workshop for Professional exam prep. This was very helpful. This is available for the Partners. If your company is a Partner, definitely ask to be enrolled to this. Studying for exams is lonely business. It was good to virtually be in a room with others and learn from the fantastic AWS instructor. Each area had a brief intro and 3 questions. Exam tips were discussed and the reasons for why an answer was correct/wrong was discussed in detail.  

 I also enrolled in cloudacademy.com and picked up portions specifically security and networking which was much better then acloudguru.

 Now in my last few weeks, I was still not feeling confident. It was then I chanced upon whizlabs.com and decided to give a try. They have 400 questions. According to them all 400 are unique. But in my experience at least 10 to15% was repeat. But that was okay. Each test has 80 questions. On completion of each test I reviewed each question irrespective of whether I got it right or wrong. Review for each question on whizlabs had explanation on why a particular choice in the answer was most suitable/unsuitable with corresponding link to AWS FAQs/docs/whitepapers/videos. Which I found very useful. I also considered variations to the problem and hence could focus on the material before me and create mind-maps/tables for different combinations. I also focused on related materials in depth. Which means a single question would lead me to hours of study in the related area. By the end of all the questions, I had criss-crossed AWS materials in many different directions.  

 The primary benefits were

1)    Helped me understand the question and answer style and how to interpret them.

2)    Get into an exam mode and focus. Progressively getting faster and more accurate.

3)    Armed with a question in mind, the same study materials provided more clarity. I was less distracted (which really helps!)

4)    Focus on a problem instead of one particular service/area. Working out how/what combination of services come together to solve a problem. Figuring out other variations in a problem and the best responses for them.

5)    Was able to focus on all areas and not get key holed into any particular one for too long.

And the last few days, re-read FAQS on EC2, DynamoDB, S3, VPC etc. For the final night walked through http://jayendrapatil.com - AWS Services Cheat Sheet.

Obviously the preparation is a combination of going through structured courses, reading whitepapers/docs/FAQs, videos, hands-on labs, practising with sample questions. It cannot be just one method. However using problem solving as the primary approach helped it to bring it altogether towards the end.

Good luck for your exam!