2 min lesson
Skeleton first, then harden
Put yourself in this case: "Designing automated PR review for a bank where no source code may leave the VPC, what do you address before sketching the happy path and how do you sequence the build?" Give the clearest next step.
Step 1 of 3
Skeleton first, then harden
Even in system design, scope a walking skeleton before you describe the production system. It shows the same instinct from the build onsite and keeps the design honest about sequencing.
- 1Skeleton. One repo, one team, model in-VPC, agent comments on a PR, human approves. End-to-end, flagged off for everyone else.
- 2Instrument. Add tracing and the eval set against that one team's history before widening. Prove quality with numbers, not vibes.
- 3Harden. SSOSingle Sign-On. One company login (usually via SAML or OIDC) instead of a separate password per tool. Press Enter for the full definition.-scoped identity, rate limits and retries with backpressure, per-failure fallbacks, cost budgets per call.
- 4Roll out. Flag on team by team, watch the eval gate and the metrics, keep the one-switch rollback live the whole way.
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Advanced table
Integrate with the legacy stack honestly
Integrate with the legacy stack honestly
Enterprises don't run greenfield. There'll be a 12-year-old CI server, a custom code-review tool, secrets in a vault three teams don't fully understand. Pretending otherwise loses credibility instantly.
- Tradeoff
- Model hosting
- Option A
- Self-host in their VPC (full control, ops burden)
- Option B
- Approved gateway with ZDRZero Data Retention. A contractual guarantee that the model provider won't store your code or train on it. Press Enter for the full definition. (less ops, must clear security)
- How you'd decide
- Their data-residency bar and whether they can run GPUs decide it.
- Tradeoff
- Latency vs. cost
- Option A
- Big model on every PR (best reviews, pricey/slow)
- Option B
- Cheap model first, escalate on uncertainty
- How you'd decide
- Tier by PR risk; reserve the expensive call for diffs that touch sensitive paths.
- Tradeoff
- Integration point
- Option A
- Native in their custom review tool (integrated, brittle)
- Option B
- Standalone bot posting comments (robust, less polished)
- How you'd decide
- Start standalone for the skeleton; go native only once value is proven.
| Tradeoff | Option A | Option B | How you'd decide |
|---|---|---|---|
| Model hosting | Self-host in their VPC (full control, ops burden) | Approved gateway with ZDRZero Data Retention. A contractual guarantee that the model provider won't store your code or train on it. Press Enter for the full definition. (less ops, must clear security) | Their data-residency bar and whether they can run GPUs decide it. |
| Latency vs. cost | Big model on every PR (best reviews, pricey/slow) | Cheap model first, escalate on uncertainty | Tier by PR risk; reserve the expensive call for diffs that touch sensitive paths. |
| Integration point | Native in their custom review tool (integrated, brittle) | Standalone bot posting comments (robust, less polished) | Start standalone for the skeleton; go native only once value is proven. |
Name both options and your reasoning. The interviewer is grading the tradeoff thinking, not the pick.
Think out loud and state your assumptions as you go: "I'm assuming no code can leave the VPC, so the model is self-hosted or behind an approved gateway - stop me if that's wrong." Then reason through the tradeoff instead of declaring a winner. Candidates who narrate their reasoning and surface failure modes unprompted consistently outscore candidates with a cleaner final diagram.