Start the interview draft with a failure packet
A useful troubleshooting interview tests how candidates reduce uncertainty, not whether they remember an obscure fix. Start with an authentic error message, then supply enough context to make investigation possible. The error should anchor the exercise without revealing its cause.
Build a small failure packet: the role level, affected system, recent change, error text, one relevant artifact, and operational constraints. Remove customer information, credentials, and proprietary implementation details before using an AI assistant to draft questions.
For each packet, request one opening question, three follow-ups, expected evidence, and a scoring rubric. Explicitly prohibit invented logs and hidden requirements. The examples below show what that structure looks like.
Q: What should “Cannot read properties of undefined” test?
Error: TypeError: Cannot read properties of undefined (reading 'id').
Drafting problem: The question becomes a JavaScript trivia quiz: “What causes this error?” That rewards recognition without exposing debugging judgment.
Better opening: “After a deployment, some account pages fail with this error. The stack trace points to a component reading account.owner.id. What would you inspect first, and what evidence would distinguish your leading explanations?”
- Provide a sanitized stack trace and two response fixtures, including one missing the owner object.
- Ask whether the missing value is permitted by the data contract.
- Ask for a regression test and a user-facing failure behavior.
Scoring signal: Strong answers separate a defensive rendering change from the upstream contract problem. Do not require optional chaining as the single correct fix; silently hiding invalid data can preserve the underlying defect.
Q: What should “deadlock detected” reveal?
Error: PostgreSQL SQLSTATE 40P01: deadlock detected.
Drafting problem: “Explain deadlocks” produces rehearsed definitions rather than evidence of database reasoning.
Better opening: “Two transaction paths update the same pair of inventory rows in different orders. Some transactions fail with this message. Sketch a possible interleaving, then propose a mitigation and explain its trade-offs.”
Include the transaction statements and relevant transaction boundaries. Follow up by asking what changes if the application retries the failed operation, and whether external side effects could be duplicated.
Scoring signal: Look for a plausible lock cycle, consistent lock ordering, and bounded retry handling that accounts for transaction rollback. Reward candidates who request the deadlock report before treating their hypothesis as proven. A senior candidate should also discuss contention and operational visibility.
Q: What should “ECONNREFUSED” measure?
Error: connect ECONNREFUSED 127.0.0.1:5432.
Drafting problem: The interviewer expects “start PostgreSQL,” but the actual scenario involves an application running inside a container.
Better opening: “The application connects successfully on a developer laptop but fails inside its container with this message. What does the address mean in each environment, and which checks would you perform?”
Supply a minimal container configuration with credentials removed. Ask candidates to distinguish a refused connection from a name-resolution failure or an authentication rejection. Do not accept disabling network controls as a complete remedy.
Scoring signal: Strong answers identify the network namespace boundary, verify the intended service address and listener, and test connectivity from the failing environment.
Q: What if the drafting assistant returns “401 Unauthorized”?
Workflow problem: The AI request fails before it can generate the interview packet. Check credential loading, the authorization format expected by the client, and the configured endpoint. Never paste a live key into the interview material or debugging transcript.
SwiftRelay is a practical option when your question-drafting workflow uses an OpenAI-compatible SDK. Configure its base URL as https://api.fastapirelay.com/v1; Claude Code and Gemini CLI use the bare host, https://api.fastapirelay.com. Billing is per token. Sign up for SwiftRelay to try drafting a sanitized interview packet with the small gift credit available to new accounts.
Check the question rubric before the hiring green light
Before using any generated question, have an engineer solve it using only the supplied packet. Fix missing context and unsupported answer assumptions. Score evidence gathering, hypothesis testing, remediation safety, and communication separately. Use the same opening materials and scoring anchors for every candidate, while allowing multiple defensible solutions.