Frontend and backend system design solve different problems.
Backend focus:
- Millions of requests per second
- Data storage and consistency
- Server scaling and load balancing
Frontend focus:
- Millions of users with varying devices and networks
- Rendering performance and interactivity
- Bundle size and browser limitations
The metrics differ: Backend cares about latency and throughput. Frontend cares about Time to Interactive and Core Web Vitals.
You're expected to think about the user experience, not just data flow.