Microservices

Microservices Interview Questions – Phase-wise Mapping

By Utility Zone · 2026-01-28T11:27:47.826141

This document maps common microservices interview questions to the learning phases and articles you completed. Use this for interview preparation, revision, and mock interviews.

Phase 1: Microservices Fundamentals

Q1. What are microservices?

  • Independently deployable services
  • Organized around business capabilities
  • Own their data

Q2. Monolith vs Microservices?

  • Deployment: Single vs Independent
  • Scaling: Whole app vs per service
  • Failure isolation

Q3. When should you NOT use microservices?

  • Small teams
  • Simple applications
  • No DevOps maturity

Phase 2: Building Microservices

Q4. What makes a service a microservice?

  • Independent deployment
  • Own database
  • Clear responsibility

Q5. Typical Spring Boot microservice structure?

  • Controller
  • Service
  • Repository
  • Configuration

Q6. How do you run multiple microservices locally?

  • Different ports
  • Separate configs
  • Profiles

Phase 3: Communication & Discovery

Q7. How do microservices communicate?

  • REST (sync)
  • Messaging (async)

Q8. Problems with REST-based communication?

  • Tight runtime coupling
  • Cascading failures
  • Latency

Q9. What is service discovery?

  • Dynamic service lookup
  • Avoids hardcoded URLs

Q10. How does Eureka work?

  • Services register themselves
  • Clients discover by service name

Phase 4: API Gateway

Q11. Why do we need an API Gateway?

  • Single entry point
  • Centralized security
  • Routing

Q12. Responsibilities of API Gateway?

  • Routing
  • Authentication
  • Rate limiting
  • Logging

Q13. Should business logic be in gateway?

  • No
  • Only cross-cutting concerns

Phase 5: Configuration & Security

Q14. What is Spring Cloud Config?

  • Centralized configuration server
  • Externalized configs
  • Git-backed

Q15. Why centralized config?

  • Avoid duplication
  • Easy environment management

Q16. How do you secure microservices?

  • JWT
  • Gateway-level security

Q17. Why JWT?

  • Stateless
  • Scalable
  • No server session

Phase 6: Data & Transactions

Q18. Why database-per-service?

  • Loose coupling
  • Independent scaling
  • Autonomy

Q19. Can microservices share a database?

  • No (anti-pattern)

Q20. Why ACID transactions don’t work in microservices?

  • Distributed systems
  • No single DB

Q21. What is Saga pattern?

  • Sequence of local transactions
  • Compensation on failure

Q22. Choreography vs Orchestration?

  • Events vs central controller

Phase 7: Event-Driven Architecture

Q23. Sync vs Async communication?

  • Blocking vs non-blocking

Q24. What is event-driven architecture?

  • Services react to events
  • Loose coupling

Q25. Kafka vs RabbitMQ?

  • Kafka: streaming
  • RabbitMQ: messaging

Q26. What is idempotency?

  • Same event processed multiple times safely

Phase 8: Observability & Resilience

Q27. What is observability?

  • Ability to understand system state

Q28. Three pillars of observability?

  • Logs
  • Metrics
  • Traces

Q29. What is distributed tracing?

  • Track request across services

Q30. What is circuit breaker?

  • Prevent cascading failures

Q31. Retry vs Timeout?

  • Retry for transient failures
  • Timeout prevents hanging calls

Phase 9: Docker & Docker Compose

Q32. Why Docker for microservices?

  • Consistency
  • Portability

Q33. Docker image vs container?

  • Image = blueprint
  • Container = running instance

Q34. Why Docker Compose?

  • Run multiple services locally

Q35. Why localhost doesn’t work in containers?

  • Each container has its own network

Phase 10: Kubernetes & System Design

Q36. Why Kubernetes?

  • Auto-scaling
  • Self-healing
  • Rolling updates

Q37. Pod vs Deployment?

  • Pod = single instance
  • Deployment = manages replicas

Q38. What is a Kubernetes Service?

  • Stable network endpoint

Q39. How do you explain a microservices project end-to-end?

  • Gateway
  • Services
  • DB per service
  • Events
  • Security
  • Deployment

Q40. Common microservices mistakes?

  • Overengineering
  • Shared DB
  • No observability

Final Tip for Interviews

When answering:

  • Always explain why, not just what
  • Use real-world examples
  • Mention trade-offs

You now have a complete microservices interview playbook.