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How do you review a design document?

AnthropicSoftware Engineer · Onsite
HardSoftware EngineerOnsiteSoftware Engineering Fundamentals

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This question assesses a candidate's ability to critically evaluate technical design documentation by identifying architectural risks, scalability bottlenecks, and gaps in operational planning.

The Scenario

You are a senior engineer at a company building a high-traffic AI inference API. A teammate has submitted a design document for a new 'Feature Flagging Service' that will allow developers to toggle new model weights or experimental UI components in real-time.

The document proposes the following architecture:

  • A centralized PostgreSQL database stores all flag states.
  • Services pull the entire configuration file (JSON) from the database every 60 seconds via a shared library.
  • If the database is unreachable, the services default to a hardcoded 'OFF' state.
  • There is no mention of caching, regional distribution, or audit logging.

The Task

Walk me through your systematic process for reviewing this design document. Identify the primary weaknesses in the proposal and explain how you would provide feedback to the author. Your answer should cover:

  1. How you evaluate if the proposed solution meets the stated business requirements.
  2. How you assess technical correctness, including reliability and failure modes.
  3. How you analyze performance and scalability at scale.
  4. How you ensure the system is maintainable and operationally ready.

Hints

Hint 1

Focus first on the 'blast radius'—what happens to the production services if the database experiences high latency or downtime?

Hint 2

Consider the difference between a 'push' and 'pull' architecture regarding consistency and the propagation delay of configuration changes.

Hint 3

Discuss the 'observability' aspect: how would a developer debug why a specific feature is enabled or disabled for a user in production?

Follow-up questions

  • How would you balance the need for immediate feature propagation against the risk of overwhelming your database with thousands of concurrent service requests?
  • If the requirement changed to support 'User-Targeted Flags' (e.g., enable for 5% of traffic), how would that change your feedback on the data model?
  • How do you approach a situation where the author disagrees with your feedback on a critical architectural bottleneck?