Comprehensive Node.js + TypeScript Interview Guide for Senior Microservice Developers

Comprehensive Node.js + TypeScript Interview Guide for Senior Microservice Developers

By Mark Kendall — LearnTeachMaster.org / BuildIt / Kendallsoft

🧭 Introduction

Hiring a great Node.js and TypeScript developer isn’t about checking syntax knowledge — it’s about finding someone who truly understands microservice architecture from end to end.

The ideal senior developer knows how to design, build, observe, and operate production-grade services that scale, recover, and evolve cleanly.

In this guide, I’ve curated 15 comprehensive interview questions (with expected answers) that help you identify real architectural maturity, not just coding familiarity. These are the same questions I use when interviewing senior developers for large-scale enterprise projects.

⚙️ 1. Service Layering and Structure

Question: How do you layer a well-designed Node.js microservice using TypeScript?

Expected Answer:

A solid service includes:

• Controllers (Routes): Entry points for HTTP requests.

• Services: Core business logic.

• Repositories: Data access or API integration.

• Models/DTOs: Define data contracts and validation schemas.

• Middleware: For cross-cutting concerns (auth, logging, validation).

• Configuration: Environment-driven settings, dependency injection.

What to Listen For: Clear separation of concerns and awareness of maintainability.

🌐 2. Stateless RESTful Design

Question: What does it mean for a REST API to be stateless?

Expected Answer:

Each request carries all the context it needs. The server doesn’t store session state — enabling horizontal scalability, failover, and simpler deployments.

🧱 3. Tenets of a Good RESTful Service

Question: What makes a web service truly RESTful?

Expected Answer:

• Resource-based URIs

• Standard HTTP verbs

• Proper use of HTTP status codes

• Statelessness

• Content negotiation

• Optional: HATEOAS, API versioning

Look For: Conceptual clarity and consistency.

🔁 4. Understanding the Node.js Event Loop

Question: Explain the Node.js event loop in simple terms.

Expected Answer:

It’s a single-threaded loop that handles asynchronous callbacks in phases. It processes timers, I/O callbacks, and other queued events without blocking.

🚫 5. Avoiding Event Loop Blocking

Question: What blocks the event loop and how do you prevent it?

Expected Answer:

CPU-heavy operations or synchronous I/O. Solutions include:

• Offloading to worker threads

• Using async/await and non-blocking libraries

• Streaming large data chunks instead of buffering

⚡ 6. Asynchronous Communication

Question: How do you implement async communication between services?

Expected Answer:

• Promises and async/await

• Event emitters

• Message brokers (Kafka, RabbitMQ)

• WebSockets for real-time

• Background jobs via queues

Look For: Pattern awareness (pub/sub, queues, async jobs).

🕓 7. Handling Long-Running Tasks

Question: How do you manage long or slow calls?

Expected Answer:

Use:

• Timeouts and retries

• Circuit breakers (Opossum)

• Message queues for decoupling

• Async job workers for heavy lifting

📊 8. Observability and Logging

Question: How do you handle observability?

Expected Answer:

• Logs: Structured (Winston, Pino) with trace IDs

• Metrics: Prometheus or OpenTelemetry

• Tracing: Jaeger, Datadog, or Tempo

• Dashboards: Grafana, CloudWatch

Listen For: Awareness of correlation IDs and distributed tracing.

🧠 9. Dependency Management in Large Codebases

Question: How do you manage dependencies and structure in large projects?

Expected Answer:

Use monorepos (Nx, Turborepo), shared internal libraries, strict semantic versioning, and automated dependency updates.

🧩 10. Type Safety and Data Validation

Question: How do you ensure strong typing and runtime safety?

Expected Answer:

• Use strict TypeScript mode

• Runtime validation via Zod or class-validator

• Shared DTOs between producer and consumer

• Avoid any and unsafe casts

🧮 11. Error Handling Strategy

Question: How do you handle errors in Express?

Expected Answer:

Centralized middleware catches all errors.

Custom error classes map to HTTP codes.

Log full stack traces internally but expose safe messages externally.

🔐 12. Configuration and Secrets Management

Question: How do you manage configurations and secrets?

Expected Answer:

Externalize configs using environment variables or a secrets manager (AWS, Vault).

No secrets in code or version control.

Support per-environment configs.

🧱 13. Security Practices

Question: What security measures do you enforce?

Expected Answer:

• HTTPS

• JWT/OAuth2 authentication

• Input validation and sanitization

• Helmet middleware

• Rate limiting and CORS

• Principle of least privilege

📦 14. Deploying to Containers and Kubernetes

Question: What are best practices for deploying Node.js microservices?

Expected Answer:

• Multi-stage Docker builds

• Health and readiness probes

• Graceful shutdown on SIGTERM

• Logging to stdout

• Resource limits in pods

🧭 15. Defining a “Good Microservice”

Question: What defines a good microservice to you?

Expected Answer:

It does one thing well, owns its data, is observable, loosely coupled, independently deployable, and resilient under failure.

💬 Closing Thoughts

Finding the right Node.js engineer means going beyond “can they code?” and asking “can they design?”

When you use these questions, focus on how candidates reason about architecture — how they keep the event loop healthy, ensure observability, and build APIs that scale.

If they light up when they talk about observability, resilience, and domain boundaries — that’s your hire.

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