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.<p>Here are previous discussions for each part:
I. <a href="https://news.ycombinator.com/item?id=37709284">https://news.ycombinator.com/item?id=37709284</a> (345 points, 188 comments)
II. <a href="https://news.ycombinator.com/item?id=37728849">https://news.ycombinator.com/item?id=37728849</a> (55 points, 2 comments)
III. <a href="https://news.ycombinator.com/item?id=37801150">https://news.ycombinator.com/item?id=37801150</a> (212 points, 106 comments)
IV. <a href="https://news.ycombinator.com/item?id=37907482">https://news.ycombinator.com/item?id=37907482</a> (57 points, 11 comments)