Start every interview by clarifying requirements. Never assume.
Functional requirements: What the system does. "Users can post tweets." "Users can follow other users."
Non-functional requirements: How well the system does it. Latency, availability, consistency, scale.
Ask questions like:
- How many users? Daily active users?
- Read-heavy or write-heavy?
- What latency is acceptable?
- Can we tolerate eventual consistency?
Spend - minutes here. It shows maturity.