Let me take you on a journey. This true story begins with a performance issue in a Ruby on Rails application, and ends deep inside internals of MRI, surrounded by barren landscape of C’s curly braces. Using tools I knew before, learning new utilities, failing to get a conclusive answer, and learning from all that, marked my passage from a software developer to a seasoned bug hunter. This talk will spare you the frustration of such a trip, and give you the raw insight.