Whoooo! I passed the GCP data engineer exam. In truth, I am not really a data engineer.. but it is a role I can fill and I strongly feel that as a data scientist you should be able to have a solid grasp of engineering too, or at least understand it well enough to know what the challenges are. The exam was about 2 hours long and is supposed to be roughly equivalent to the AWS professional level certifications. Funny enough, it actually covers a lot of the ML engineering topics. Perhaps there's a ML exam in the works?
*Update: As of 2020 there is now a GCP Machine Learning certification. I passed it in 2021. You can read more about it here
I suppose I got lucky with the matter. I've been working with GCP for about a year now and I've mostly been involved whenever there's a ML demand.
As for studying strategies: I had a four-day training back in August. After that, I spent about 20 hours doing coursera courses and about 16 studying with the exam guide as my guideline. Particularly the last part was vital.
You can check out the certification here: https://www.credential.net/a015b522-77d3-48c0-b7f7-16c9948a9ac4