# System design assessment: evaluate decisions, not diagrams

https://lunaprompts.com/solutions/system-design-assessment

Illustrative assessment template. Adapt and calibrate for the role before use.

A useful architecture explains the requirements, the tradeoffs, and what happens when something breaks.

## Task

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.

## Deliverables

- 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

## Suggested rubric

### Requirements and assumptions — 25%
Stronger evidence: Separates hard requirements from assumptions and checks them before choosing components.
Investigate: Chooses a stack before clarifying the workload.

### Data and access boundaries — 30%
Stronger evidence: Explains tenant isolation, document lifecycle, and authorization in the retrieval path.
Investigate: Relies on a prompt to prevent cross-tenant access.

### Reliability and operations — 25%
Stronger evidence: Defines degradation, observability, and recovery behavior for concrete failures.
Investigate: Names redundant components without describing a failure sequence.

### Tradeoffs and evolution — 20%
Stronger evidence: Connects cost, latency, and complexity to stated workload assumptions.
Investigate: Uses scale claims without quantities or explains only the ideal design.

## Illustrative report (not a real candidate result)

The illustrative design separates customer indexes, but has no plan to invalidate retrieved passages after a document is deleted.

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.

## Follow-up questions

- 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?

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