Top 50 Spring Boot Interview Questions and Answers for 2026

Spring Boot remains one of the most sought-after skills for Java developers. Whether you're a fresher or an experienced engineer, interviewers frequently ask Spring Boot questions ranging from basic concepts to production-level scenarios.

In this guide, we'll cover the most commonly asked Spring Boot interview questions.

1. What is Spring Boot?

Spring Boot is a framework built on top of Spring that simplifies application development by reducing configuration and setup requirements.

Benefits:

• Faster development

• Embedded servers

• Production-ready features

• Auto Configuration

2. What Problems Does Spring Boot Solve?

Traditional Spring applications required:

• XML configuration

• Manual dependency setup

• Complex server deployment

Spring Boot simplifies all of these.

3. What is Auto Configuration?

Auto Configuration automatically configures beans based on dependencies available in the classpath.

For example:

If Spring Boot detects a database dependency, it automatically creates datasource configurations.

4. What is Starter Dependency?

Starter dependencies provide pre-configured libraries.

Examples:

• spring-boot-starter-web

• spring-boot-starter-data-jpa

• spring-boot-starter-security

• spring-boot-starter-test

5. What is @SpringBootApplication?

It combines:

@Configuration
@EnableAutoConfiguration
@ComponentScan

into a single annotation.

6. Difference Between @Component and @Bean?

@Component

Automatically detected during component scanning.

@Bean

Manually defined inside configuration classes.

7. What is Dependency Injection?

Dependency Injection allows Spring to create and manage object dependencies automatically.

Example:

@Service
public class UserService {

    private final UserRepository repository;

    public UserService(UserRepository repository){
        this.repository = repository;
    }
}

8. Constructor Injection vs Field Injection?

Constructor Injection is preferred because:

• Better testability

• Immutable dependencies

• Easier maintenance

9. What is Bean Scope?

Common scopes:

• Singleton

• Prototype

• Request

• Session

Singleton is default.

10. What is Spring IoC Container?

IoC (Inversion of Control) container manages bean lifecycle and dependency injection.

11. What is REST API?

REST APIs expose application functionality through HTTP methods.

Methods:

• GET

• POST

• PUT

• DELETE

• PATCH

12. Difference Between PUT and PATCH?

PUT

Updates entire resource.

PATCH

Updates partial resource.

13. What is ResponseEntity?

ResponseEntity allows customization of:

• Status code

• Headers

• Response body

Example:

return ResponseEntity.ok(user);

14. What is Global Exception Handling?

Centralized exception handling using:

@RestControllerAdvice

Benefits:

• Consistent responses

• Cleaner code

• Better maintainability

15. What is Spring Data JPA?

Spring Data JPA simplifies database operations by reducing boilerplate code.

16. Difference Between CrudRepository and JpaRepository?

JpaRepository provides:

• Pagination

• Sorting

• Batch operations

in addition to CRUD operations.

17. What is Lazy Loading?

Associated data loads only when needed.

Improves performance.

18. What is Eager Loading?

Associated data loads immediately.

Useful when related data is always required.

19. What Causes N+1 Query Problem?

Occurs when fetching parent records and repeatedly querying child records.

Common JPA performance issue.

20. How Do You Solve N+1 Problem?

Solutions:

• Fetch Join

• Entity Graph

• DTO Projection

21. What is Actuator?

Spring Boot Actuator provides production monitoring endpoints.

Examples:

• /health

• /metrics

• /info

22. What is Spring Security?

Framework for:

• Authentication

• Authorization

• Session management

23. What is JWT?

JSON Web Token is used for stateless authentication.

Structure:

• Header

• Payload

• Signature

24. How Does JWT Authentication Work?

1. User logs in.

2. Server generates token.

3. Client stores token.

4. Token sent with every request.

5. Server validates token.

25. What is CORS?

Cross-Origin Resource Sharing allows frontend applications hosted on different domains to access APIs.

26. What is Microservice Architecture?

Architecture where applications are split into independent deployable services.

27. What is API Gateway?

API Gateway acts as a single entry point for all client requests.

Benefits:

• Routing

• Security

• Rate limiting

28. What is Service Discovery?

Allows services to locate each other dynamically.

Popular tool:

Netflix Eureka.

29. What is Circuit Breaker?

Prevents repeated calls to failing services.

States:

• Closed

• Open

• Half Open

30. What is Resilience4j?

Popular library for:

• Circuit Breaker

• Retry

• Rate Limiter

• Bulkhead

Production Questions Frequently Asked

31. How Do You Handle High Traffic APIs?

• Caching

• Load Balancing

• Database Optimization

• Horizontal Scaling

32. How Do You Improve API Performance?

• Redis Cache

• Pagination

• Database Indexing

• Async Processing

33. What Monitoring Tools Have You Used?

Examples:

• Prometheus

• Grafana

• ELK Stack

• Splunk

34. How Do You Secure Sensitive Configuration?

Use:

• Environment Variables

• Vault Solutions

• Secret Managers

Never hardcode secrets.

35. Explain a Production Issue You Solved

Interviewers often focus heavily on:

• Root cause analysis

• Troubleshooting process

• Preventive measures

Real-world examples carry significant weight during interviews.

Final Thoughts

Spring Boot interviews today focus on much more than annotations and theory.

Companies expect developers to understand:

• Microservices

• Security

• Performance Optimization

• Monitoring

• Production Support

• Cloud Deployments

Practicing these questions through realistic mock interviews can significantly improve your confidence and interview performance.

The more you practice explaining concepts verbally, the better prepared you'll be for real interviews.