This story was pushed off the front page by three stories that had steadily declined to page 4 over several hours, then suddenly jumped to the front page in 5 minutes.

http://hnrankings.info/8311860,8312295,8312249,8312411/

  #162 -> #25   Server Migration with Zero Downtime
  #135 -> #11   Show HN: Pup – A command line HTML parser
  #127 -> #23   The Impossible Star

Edit: HN moderator response in this thread, https://news.ycombinator.com/item?id=8313505