I can only go by what FB people have told me in person and that was "we use MySQL pretty much just as a k/v store". I think all the people I talked to worked on

I can only go by what FB people have told me in person and that was "we use MySQL pretty much just as a k/v store". I think all the people I talked to worked on the frontend rather than MySQL directly though, so if you worked with MySQL directly that seems more authoritative.