You ARE expected to know:
- Client-server architecture (browser talks to server)
- What APIs are and how REST works
- Basic database concepts (SQL vs NoSQL, when to use each)
- How HTTP requests work
- What caching means and why it helps
You are NOT expected to know:
- Distributed systems theory
- Specific technologies (Kafka, Redis internals)
- Exact capacity calculations
- How to handle millions of requests per second
Your interviewer knows your experience level. They're checking whether you can think systematically, not whether you've built systems at Google scale.