Error Handling & Observability Interview Questions

Use next(err) to forward errors to error-handling middleware or wrap async handlers to catch rejections.

Structured JSON logs, correlation IDs, proper log levels, and using a log shipper to central systems.

Use OpenTelemetry SDK to instrument requests, propagate context via headers, and export traces to a backend like Jaeger.

Use unit tests with mocks or fakes for external dependencies, integration tests against a real database or message broker when appropriate, and contract tests for APIs. Error Handling & Observability should have clear inputs/outputs so tests remain fast and deterministic.

Log structured events with correlation IDs, track latency and error rates, and alert on SLO breaches. For Error Handling & Observability, capture enough context to reproduce failures without logging secrets such as passwords or tokens.

Auth often gates access to endpoints or resources that rely on Error Handling & Observability. Apply least privilege, validate tokens or sessions at the boundary, and never trust client-side checks alone. Mention OAuth, JWT, or session cookies as appropriate to the stack.

Separate config from code using environment-specific settings, secrets managers, and twelve-factor practices. Document required variables for Error Handling & Observability so deployments to staging and production remain repeatable and auditable.

Consider idempotency, status codes, pagination, versioning, and error payloads. Error Handling & Observability should not leak internal exceptions to clients; return consistent error shapes and document them in OpenAPI or similar specs.

Catch exceptions at appropriate layers, map them to user-safe messages, retry transient failures with backoff where suitable, and record failures for operators. Avoid swallowing errors silently—failed Error Handling & Observability operations should be visible in logs and metrics.

Use the official Node.js docs for Error Handling & Observability, language or framework references, and reputable community guides. Bookmark release notes and migration guides when upgrading versions, since Error Handling & Observability behavior can change between releases.

Copying snippets without understanding why Error Handling & Observability works leads to fragile code. Beginners often skip error handling, tests, or edge cases. Slow down, trace execution step by step, and validate assumptions with small experiments.

Error Handling & Observability may touch request handling, business logic, persistence, or integrations. Knowing that placement helps you debug production issues and design secure, testable APIs.

Validate tokens or sessions at the boundary, apply least privilege, and never trust client-only checks. Mention OAuth, JWT, or cookies as appropriate to the stack.

Start with the problem Error Handling & Observability solves, show a minimal working example, and list the team conventions around it. Point them at official docs and one trusted internal example rather than random snippets.

Error Handling & Observability shows up often in production Node.js work—misunderstanding it leads to bugs, performance issues, or security gaps. Interviewers want clear explanations plus practical judgment.

Follow team conventions, split concerns into testable units, handle edge cases, and document assumptions. Review similar modules in the codebase, add observability, and ship incrementally with feature flags if Error Handling & Observability is risky.

Map the Error Handling & Observability attack surface (injection, broken auth, data exposure, DoS). Layer defenses—validation, rate limits, least privilege, encryption, and regular audits.

One approach optimizes simplicity and time-to-market; the other optimizes performance, flexibility, or compliance. Choose based on team skill, traffic, and maintenance horizon—there is rarely a single best answer for Error Handling & Observability.

Use expand/contract or strangler patterns, dual-write/dual-read where needed, feature flags, and rollback plans. Validate parity with shadow traffic before decommissioning the old Error Handling & Observability path.

State whether Error Handling & Observability needs strong consistency or can tolerate eventual consistency. Discuss partitions, quorum, conflict resolution, and user-visible anomalies during failures.