For senior roles, interviewers evaluate: (1) **System Thinking**: How does this code affect memory, CPU, GC? (2) **Design Patterns**: Can you apply SOLID principles? (3) **Observability**: How will you debug/monitor this in production? (4) **Scalability**: How does this perform with 100 users? 1 million users? (5) **Trade-offs**: Can you make intelligent choices between options?
Think like an architect, code like a craftsman. Communicate your reasoning, not just syntax.