For years, people have constructed cairns, a human-made stack of stones, as landmarks, monuments or tributes. These days, hikers will add a rock to a cairn as they reach a summit of a mountain or a turning point on a trail. The longer one sits across from Khalid Halim in Reboot’s San Francisco office, the more one realizes his sofa is a modern day cairn. Instead of stones, well-known tech leaders, angels and VCs have dropped their guard there—along with their stories, ambitions and fears. It marks the start of many technologists’ inflection points.