As part of my role at VMware, vSAN is a core focus area of mine.
I originally completed the vSAN specialist certification at VMworld US in 2017. Today I managed to get a chance to take the newly updated 2019 version.
The 2019 vSAN specialist certification comprises of a single 2 hour 60 multi-choice question exam. It was a very enjoyable test with a mixture of design, product theory, and operational questioning.
The style of the exam is similar to a VCP (In fact it assumes an active VCP-DCV), It is based on vSAN 6.7 / 6.7U1 and concentrates on the tasks a vSAN admin needs to know to run a production platform.
As shown below in my objective checklist the exam blueprint gives an overview of the areas to concentrate on.
A good method of study for this exam would be to take each objective,
- Understand the use case from a business perspective (DR, Performance )
- Review the design decisions from the VMworld videos, or deep dive guide.
- Practice related operational tasks using a session on the VMware Hands-on labs.
- Review the use of the vSAN release notes. interoperability guide, HCL.
- Review vSAN tooling ( Sizing tools, vROps, Support insight, pro-active alerts).

I would expect someone who has some real hands-on experience with day to day vSAN tasks and exposure to good infrastructure design could pass this test with some theory study and lab practice.
As an architect, I would recommend anyone who is looking to design or help a team support vSAN to have a go at the certification for validation of skils.
A list of resources I would recommend reviewing prior to the exam is shown below.