What to collect
- An architecture diagram with trust boundaries and data flow
- A short capacity estimate with explicit assumptions and the main cost drivers
- A failure walkthrough covering stale data, cross-tenant access, and provider downtime
SYSTEM DESIGN
System design assessment: evaluate decisions, not diagrams
A useful architecture explains the requirements, the tradeoffs, and what happens when something breaks.
01 / THE TASK
A practical starting point.
Design a document-answering service for multiple customer organizations. Users upload documents and ask questions with citations. Organizations must not see one another’s documents. Explain ingestion, retrieval, updates, deletion, and an outage of the model provider. State your own traffic and latency assumptions before sizing the design.
Adapt this example to the role, agree allowed tools, and give candidates the same instructions. It is a starting template, not a validated selection test.
02 / THE RUBRIC
Agree what good looks like.
Calibrate these suggested weights with your interviewers before the first candidate. Record the evidence behind each rating.
| Criterion | Weight | Stronger evidence | Needs investigation |
|---|---|---|---|
| Requirements and assumptions | 25% | Separates hard requirements from assumptions and checks them before choosing components. | Chooses a stack before clarifying the workload. |
| Data and access boundaries | 30% | Explains tenant isolation, document lifecycle, and authorization in the retrieval path. | Relies on a prompt to prevent cross-tenant access. |
| Reliability and operations | 25% | Defines degradation, observability, and recovery behavior for concrete failures. | Names redundant components without describing a failure sequence. |
| Tradeoffs and evolution | 20% | Connects cost, latency, and complexity to stated workload assumptions. | Uses scale claims without quantities or explains only the ideal design. |
03 / ILLUSTRATIVE REPORT
From observation to follow-up.
Example only · not a real candidate resultObserved
The illustrative design separates customer indexes, but has no plan to invalidate retrieved passages after a document is deleted.
Reviewer’s next step
Walk through deletion from upload storage to retrieval caches. Ask what the user sees while the deletion propagates and how the team would verify completion.
Ask about their own work.
- What changes if traffic grows tenfold but the latency target stays the same?
- Where is tenant access checked, and how would you test that boundary?
- What happens to citations when a source document changes or is deleted?
04 / SEE THE PRODUCT
Bring the brief to your demo.
This LunaPrompts product walkthrough introduces the assessment workflow. Ask the team to demonstrate your exact task, chosen tools, and report requirements in the environment you plan to use.
The walkthrough shows the product. It is not a recording of the illustrative exercise above or an independent performance benchmark.
Read the detailed workflow guide ↗PUT IT TO WORK
Start with the role you’re hiring for.
Bring a job description, a few must-have skills, and your hiring timeline. We’ll help you shape the evaluation.
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