I found the first part of this series in HN's front page a while ago, but I think Part IV was missing back then. It's now fully published - this link is its intro + index.
Here are previous discussions for each part:
I. https://news.ycombinator.com/item?id=37709284 (345 points, 188 comments)
II. https://news.ycombinator.com/item?id=37728849 (55 points, 2 comments)
III. https://news.ycombinator.com/item?id=37801150 (212 points, 106 comments)
IV. https://news.ycombinator.com/item?id=37907482 (57 points, 11 comments)
