I tested cweagans/bg-sync over the weekend with Drupal 8 (including loads of additional dependencies managed by Composer), and got the exact same results (> 10x performance improvement measured by ApacheBench). The reason I’m interested in this approach above the others is the same as what’s listed in the why not use x section of the README. Namely, my entire reason for wanting to use Docker is to contain as many dependencies as possible, leaving my host machine as clean as possible. In this case, all the syncing happens from within the bg-sync container. Of course I’d prefer the filesystem latency issues fixed in OSXFS, but until then, this solution is perfect for my use.