System Design Card 359 — Requirements Clarification / Implement
Concern
Every design starts with defining what must be true for the system to be considered successful. A notification system for security alerts is a different system from a marketing fanout service even if both 'send messages'.
What Implement means for this concern
In BASIC, the Implement step is where you walk the design into existence in a controlled order, deepening the risky parts first. For Requirements Clarification, that means the candidate should make this concern visible at the right moment instead of bolting it on at the end.
Design move
A good move is to transcribe the plan instead of improvising. Tie the concern back to the user flow, the workload, and the dominant trade-off. That keeps the design grounded and makes it easier for the interviewer to follow why a cache, queue, replica, partition, or rate limiter is actually necessary.
Common miss
The common miss is skipping functional and non-functional requirements and drawing architecture into a vacuum. BASIC helps because the staged flow keeps this concern proportional to the prompt and connected to the rest of the architecture.
BASIC prompt
“When I reach the Implement stage, how does Requirements Clarification change the architecture, the trade-offs, or the review checklist?”