Lead with the trade-offs, not the benefits. Anyone can list microservice advantages; showing you understand the costs demonstrates real experience.
Best answers acknowledge that monoliths are often the right starting point. Microservices make sense when teams need independent deployment, different scaling profiles, or technology diversity. Hidden costs include: distributed debugging, network latency, data consistency challenges, operational overhead, and the need for service discovery, circuit breakers, and distributed tracing.
Senior-level question. Red flag: advocating microservices without acknowledging complexity. Good sign: discussing when a monolith is better and the organisational prerequisites for microservices.