Top 50 Spring Boot Microservices Interview Questions and Answers for 2025

 Here is a list of 50 Spring Boot microservices interview questions with concise answers. 



1. What are microservices?

Microservices are a software architecture style where an application is divided into small, independent services that can be deployed, managed, and scaled individually.

2. What are the advantages of microservices?

  • Scalability
  • Independent deployment
  • Flexibility in technology stack
  • Fault isolation
  • Easier maintenance and updates

3. What is Spring Boot?

Spring Boot is a framework that simplifies the process of building and deploying Spring-based applications. It provides built-in features such as embedded servers, configuration management, and production-ready features.

4. What is the difference between Spring Boot and Spring Framework?

  • Spring Boot simplifies the setup of Spring applications with embedded servers and auto-configuration.
  • Spring Framework requires manual setup of configurations, application contexts, and server setups.

5. What are Spring Boot Starter Projects?

Spring Boot starters are a set of convenient dependency descriptors to simplify your build configuration. For example, spring-boot-starter-web helps in creating web applications.

6. Explain the architecture of Spring Boot microservices.

  • Spring Boot microservices follow a distributed architecture where each service focuses on a specific business functionality.
  • They communicate via REST APIs or messaging systems.
  • Services can be independently deployed, scaled, and updated.

7. How does Spring Boot handle configuration management?

Spring Boot uses application.properties or application.yml for configuration. It also supports external configuration through environment variables or config server.

8. What is Spring Cloud?

Spring Cloud is a collection of tools designed to facilitate the development of distributed systems and microservices. It provides features like service discovery, circuit breakers, routing, and configuration management.

9. What is Netflix Eureka?

Eureka is a service registry from Netflix used in microservices architecture for service discovery. Microservices register themselves with Eureka, and other services can find them by querying the registry.

10. What is a Spring Cloud Config Server?

Spring Cloud Config Server is a tool that provides centralized configuration management for Spring Boot applications across environments, supporting git, SVN, or file-based repositories.

11. What is Spring Cloud Netflix Ribbon?

Ribbon is a client-side load balancer used for distributing requests to different instances of a microservice. It integrates with Eureka for dynamic service discovery.

12. What is Spring Cloud Netflix Hystrix?

Hystrix is a circuit breaker pattern implementation that helps prevent failures in distributed systems by isolating points of access to remote services.

13. What is Spring Cloud Gateway?

Spring Cloud Gateway is an API gateway built on top of Spring WebFlux. It is used to route requests to various microservices and handle cross-cutting concerns like authentication, logging, and rate limiting.

14. What are Spring Boot profiles?

Profiles allow you to define different configurations for different environments (e.g., dev, test, prod). You can activate a profile using spring.profiles.active in the application properties.

15. What is Spring Boot Actuator?

Spring Boot Actuator provides production-ready features to monitor and manage Spring Boot applications, including health checks, metrics, and application information endpoints.

16. What are the commonly used Spring Boot annotations?

  • @SpringBootApplication
  • @RestController
  • @RequestMapping
  • @Value
  • @EnableAutoConfiguration

17. What is the use of @SpringBootApplication annotation?

It is a combination of @Configuration, @EnableAutoConfiguration, and @ComponentScan annotations, which simplifies the setup of a Spring Boot application.

18. What is service discovery in microservices?

Service discovery allows microservices to find and communicate with each other without needing hardcoded addresses, typically using tools like Eureka or Consul.

19. How do microservices communicate with each other?

Microservices typically communicate via REST APIs, message brokers (e.g., RabbitMQ, Kafka), or gRPC.

20. What is API Gateway?

An API Gateway is a server that acts as an entry point into the system, routing requests to the appropriate backend services and handling concerns like authentication, rate limiting, and logging.

21. What is Spring Data JPA?

Spring Data JPA simplifies database operations by providing easy-to-use interfaces for JPA (Java Persistence API). It handles most of the CRUD operations with minimal code.

22. What is Spring Cloud Stream?

Spring Cloud Stream is a framework for building event-driven microservices that can send and receive messages to/from message brokers like RabbitMQ, Kafka, and others.

23. What is a Circuit Breaker in microservices?

A circuit breaker is a design pattern used to detect failures and prevent them from propagating through the system. It is implemented using libraries like Netflix Hystrix.

24. What is distributed tracing?

Distributed tracing is a method to track requests as they flow through various services in a microservices architecture. Tools like Zipkin and Sleuth can be used for this purpose.

25. How can you secure a microservice in Spring Boot?

You can secure microservices by using Spring Security, OAuth2, JWT (JSON Web Tokens), and implementing proper role-based access control (RBAC).

26. What is the difference between monolithic and microservices architectures?

  • Monolithic architecture: A single, tightly coupled application.
  • Microservices architecture: A collection of loosely coupled, independent services that communicate over a network.

27. How do you manage transactions in microservices?

  • Local transactions: Each microservice manages its own database transactions.
  • Distributed transactions: Use Saga pattern or two-phase commit to manage transactions across services.

28. What is the Saga pattern?

The Saga pattern is used for managing distributed transactions in microservices. It breaks a transaction into smaller, isolated transactions that are compensated in case of failure.

29. How do you handle failures in microservices?

  • Retry logic
  • Circuit breakers
  • Fallback mechanisms
  • Compensating actions
  • Event-driven architecture

30. What is the role of load balancing in microservices?

Load balancing ensures that requests are distributed evenly across multiple instances of a microservice, improving performance and availability.

31. What is the difference between synchronous and asynchronous communication in microservices?

  • Synchronous communication: One service waits for the response from another service before continuing. Example: RESTful APIs.
  • Asynchronous communication: Services do not wait for a response and can continue processing. Example: Message queues (Kafka, RabbitMQ).

32. What is the role of an API Gateway in microservices?

An API Gateway acts as a reverse proxy, routing requests from clients to the appropriate microservices. It can also handle cross-cutting concerns like authentication, rate limiting, logging, and caching.

33. What is the Circuit Breaker pattern, and how does it work in Spring Cloud?

The Circuit Breaker pattern is used to prevent failures from cascading by temporarily halting requests to a service that is likely to fail. In Spring Cloud, it is implemented using Netflix Hystrix or Resilience4j.

34. What is the role of Spring Cloud Config Server in microservices?

Spring Cloud Config Server is responsible for providing externalized configuration to all microservices in a distributed system. It helps manage configuration properties centrally and supports multiple environments.

35. What is Spring Cloud Sleuth?

Spring Cloud Sleuth is a library used for distributed tracing, providing unique trace and span IDs to track requests across microservices, helping developers debug and monitor interactions.

36. What is the role of Spring Security in microservices?

Spring Security provides authentication and authorization mechanisms in microservices. It can be used for securing REST APIs with OAuth2, JWT, and other security protocols.

37. What is OAuth2 and how does it work in Spring Boot microservices?

OAuth2 is an authorization framework that allows a user to grant limited access to resources without sharing their credentials. In Spring Boot, OAuth2 is often used for securing microservices with token-based authentication (JWT).

38. What is JWT (JSON Web Token)?

JWT is an open standard for securely transmitting information between parties as a JSON object. It is widely used for authentication and authorization in microservices architectures.

39. How do you implement service discovery in Spring Boot?

Service discovery is implemented using Spring Cloud Eureka or Consul. Eureka allows microservices to register themselves and discover others at runtime, enabling dynamic routing.

40. What are Spring Boot Auto-configurations?

Auto-configuration is a mechanism in Spring Boot that automatically configures application components based on the dependencies present in the classpath. It reduces the need for manual configuration.

41. What is a message broker in microservices, and why is it used?

A message broker is a middleware that facilitates communication between microservices by sending and receiving messages asynchronously. Popular brokers include RabbitMQ and Kafka. They are used to decouple services and provide reliable messaging.

42. What is Spring Cloud Bus?

Spring Cloud Bus is used to link and broadcast state changes (like configuration updates) across a cluster of microservices, ensuring that changes are communicated to all instances in a distributed system.

43. What is Spring Boot embedded server?

Spring Boot includes embedded servers like Tomcat, Jetty, and Undertow, which allow Spring Boot applications to run as standalone applications without needing an external server.

44. What is Spring Boot's @RestController annotation?

@RestController is a convenience annotation in Spring Boot that combines @Controller and @ResponseBody. It is used to define a controller class in a RESTful web service where the return values are automatically converted to JSON or XML.

45. What is Spring Boot's @RequestMapping annotation?

@RequestMapping is used to map HTTP requests to handler methods of MVC and REST controllers. You can specify the URL, HTTP method (GET, POST, etc.), and parameters.

46. What is the difference between @Component, @Service, and @Repository annotations in Spring Boot?

  • @Component: A general-purpose annotation for any Spring-managed bean.
  • @Service: A specialization of @Component used for service-layer components.
  • @Repository: A specialization of @Component used for DAO (Data Access Object) components.

47. What is Spring Boot's @EnableAutoConfiguration annotation?

@EnableAutoConfiguration tells Spring Boot to automatically configure the application based on the libraries on the classpath. It reduces the need for explicit configuration.

48. What is the difference between @Configuration and @Component in Spring Boot?

  • @Configuration: Used for Java-based configuration classes, often containing beans.
  • @Component: Marks a generic Spring-managed bean, used in most components like services, repositories, and controllers.

49. What is the Spring Boot @Value annotation?

@Value is used to inject values into fields in a Spring-managed bean. You can use it to inject properties from configuration files, environment variables, or default values.

50. How does Spring Boot handle database integration?

Spring Boot integrates with databases using Spring Data JPA or JDBC templates. It provides automatic configuration for database connections, transactions, and repositories.

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