Jeff, here. I put this up in time for folks coming to Spark Summit East in the hope that the influx of Spark folks to NYC might want to think a bit about my favorite type of distributed system: machine learning.<p>Even though this thing is already pretty lengthy, I still feel like there's a lot more that could be explored here. See the open questions at the end of the post. Would love to hear the feedback from the HN folks about designing reactive machine learning systems.