You are ready when you can perform across different system shapes, not when you finish reading.
Design a distributed rate limiter for API keys, with burst support and per-region enforcement.
Design a ranked news feed for users who follow both ordinary accounts and celebrity accounts.
Design a notification system that supports email, push, and SMS with preferences and retries.
Take any capstone and explain how you would migrate from the simple version to the scaled version.
| Requirement | Pass threshold | Retake rule | Why it matters |
|---|---|---|---|
| All seven rubric dimensions | At least 3 out of 4. | Retry only the low dimension first. | A single weak dimension can sink a strong technical answer. |
| One full diagram | Readable in under two minutes. | Redraw with fewer boxes and clearer paths. | The interviewer needs a stable shared picture. |
| One deep dive | Explains what breaks first and what fixes it. | Pick a higher-pressure subsystem. | Depth shows judgment better than broad component naming. |
| One recovery moment | Names the issue and redirects calmly. | Practice Chapter 22 recovery lines. | Real interviews include pushback and ambiguity. |
One 35-45 minute spoken answer, including clarification, estimate, sketch, deep dive, follow-up, and close.
One clean architecture diagram annotated with hot path, side path, and bottleneck.
Scores for all seven dimensions, strongest signal, weakest signal, and retry target.