Great breakdown of the "IO bound Rails app" myth! I really appreciate the focus on profiling and understanding actual application behavior rather than relying on assumptions. The points about threading, database interactions, and context-switch overhead are spot on and offer a fresh perspective on how performance issues are often misunderstood.

It's interesting how easy it is to default to surface-level fixes instead of addressing the root cause. Have you thought about adding a case study or some benchmarks for common workloads? It could really help teams put these ideas into practice.