Google Developers Groups (GDG) is a site designed for and around the developer community. This can be a great place to find candidates however a lot of recruiter do not search here. The reason is simple they do not know how. Well to do this without worry you need go no further than into your bag of tricks and pull out an old tried and true tool, a simple search with some extras, and a whole lot of website searching
So to source within GDG you simply need to use a skill known as xraying, like the one below.
site:gdg.community.dev/u/ data engineering
Then use your social detective skills and you are set.
Also keep in mind search in both Bing and google as the result sometimes is better in one than the other.
If you need more info on X-raying see my blog post http://www.recruitingblogs.com/profiles/blogs/seeing-what-is-really...
Until next week may the source be with you!!