181: System Design - Timed Checkpoint
Assessment
Complete a 45-minute design interview with requirements, estimates, architecture, APIs, data model, scaling plan, observability, security, and tradeoffs.
Required evidence
- clarification before solution;
- one request and one failure sequence;
- explicit consistency and availability choices;
- bottleneck and mitigation;
- honest limits and follow-up questions.
Self-review
Score clarification, correctness, completeness, communication, and tradeoff quality separately. A design can be technically plausible and still fail because it ignored authorization, data deletion, observability, or the user's latency requirement.
45-minute protocol
Spend 5 minutes on actors and success criteria, 5 on traffic/storage estimates, 10 on APIs and data ownership, 10 on the simplest architecture, 8 on one hot path and one failure path, and 7 on tradeoffs and questions. Use a consistent trace: request, auth, validation, storage/queue, response, and asynchronous effects. Say when a number is an assumption and revise it when the interviewer changes scale.
Scoring rubric
Score 0-4 in each category: requirements, estimates, API/data model, architecture, consistency/reliability, security/observability, and communication, for 28 points. A strong pass is 20+ with no zero in security or failure handling. Required edge probes are duplicate writes, unauthorized access, dependency timeout, hot key, deletion/retention, cache staleness, and deploy rollback. End with two follow-up questions and one deliberate simplification.