When my team interviews junior engineers we mainly focus on coding questions. When we interview senior engineers we tend to spend about half the time on design

When my team interviews junior engineers we mainly focus on coding questions. When we interview senior engineers we tend to spend about half the time on design questions, many of which involve no coding at all. This is because the important difference between a junior and senior engineer is not coding skill -- it is the ability to implement solutions that work properly, fulfill the requirements, and are scalable and fault tolerant. Junior candidates can sometimes do that, but most of the time they don't know when a design lacks fault tolerance or has scalability problems. When design flaws are pointed out, they don't know how to fix them or how to defend them as better trade-offs compared to the alternatives. It takes a bit experience to be able to do that -- especially experience fixing things that went wrong.