Stay ahead with the latest features and patterns in the most popular Java framework.

Spring Boot remains the most in-demand Java framework for building microservices, REST APIs, and enterprise applications. With the 2025 job market demanding developers who are proficient in Spring Boot 3.2+, understanding its latest features, patterns, and best practices is key to landing your next role.

In this article, we’ll cover essential Spring Boot interview questions (and their detailed answers) that you’re likely to encounter in 2025—ranging from beginner to advanced.

Beginner-Level Questions

1. What is Spring Boot and how is it different from Spring Framework?

Answer:
Spring Boot is a convention-over-configuration framework built on top of Spring. It simplifies the development of production-ready Spring applications by:

• Eliminating boilerplate configurations
• Providing embedded servers (Tomcat, Jetty)
• Offering auto-configuration and starter dependencies

It allows rapid application development without needing to write XML config files or manage complex setups.

2. What’s new in Spring Boot 3.x?

Answer:

• Native compilation support with GraalVM
• Based on Spring Framework 6, which uses Jakarta EE 10
• Enhanced Observability with Micrometer 2
• Improved support for virtual threads (via Project Loom)
• Modularization and Ahead-of-Time (AOT) compilation

3. How does Spring Boot auto-configuration work?

Answer:
Spring Boot uses the @EnableAutoConfiguration annotation (included in @SpringBootApplication) to scan the classpath and auto-configure beans. For example, if spring-boot-starter-web is present, Spring Boot configures embedded Tomcat and DispatcherServlet automatically.

You can customize or exclude configurations using:

@SpringBootApplication(exclude = DataSourceAutoConfiguration.class)

Intermediate-Level Questions

4. What is Spring Boot Actuator and how is it used?

Answer:
Spring Boot Actuator provides production-ready endpoints to monitor and manage applications.

Examples:

• /actuator/health
• /actuator/metrics
• /actuator/env

It integrates with tools like Prometheus, Micrometer, and Grafana.

management.endpoints.web.exposure.include=health,info,metrics

5. How do you secure a Spring Boot REST API?

Answer:
Use Spring Security and define a SecurityFilterChain:

@Bean
public SecurityFilterChain securityFilterChain(HttpSecurity http) throws Exception {
 return http
 .authorizeHttpRequests(auth -> auth
 .requestMatchers("/public/**").permitAll()
 .anyRequest().authenticated())
 .oauth2ResourceServer(OAuth2ResourceServerConfigurer::jwt)
 .build();
}

You can integrate with OAuth2, JWT, LDAP, or even custom authentication providers.

6. What are Spring Boot Starters?

Answer:
Starters are a set of convenient dependency descriptors to include common functionality. For example:

• spring-boot-starter-web – Web + Tomcat
• spring-boot-starter-data-jpa – JPA + Hibernate
• spring-boot-starter-security – Spring Security

They remove the need to manually declare individual dependencies.

7. How do you externalize configuration in Spring Boot?

Answer:
Spring Boot reads properties from:

• application.properties or application.yml
• Environment variables
• Command-line arguments
• Config servers (in Spring Cloud)

You can bind configs to POJOs using @ConfigurationProperties.

Advanced-Level Questions

8. How do you build native Spring Boot apps using GraalVM?

Answer:
Native images improve startup time and reduce memory footprint.

Steps:

• Use the spring-boot-starter-native
• Add the AOT plugin:

<plugin>
 <groupId>org.graalvm.buildtools</groupId>
 <artifactId>native-maven-plugin</artifactId>
</plugin>

• Run: ./mvnw spring-boot:build-image -Pnative

9. Explain Spring Boot Observability and Micrometer.

Answer:
Spring Boot integrates with Micrometer to collect metrics, logs, and traces. With Spring Boot 3, observability is a first-class citizen.

Example metrics:

• JVM memory usage
• HTTP request latency
• Database connection pool status

You can export data to Prometheus, New Relic, Datadog, etc.

10. How do you implement multi-module architecture in Spring Boot?

Answer:
Split your codebase into:

• core (shared business logic)
• api (REST interfaces)
• service (business logic implementation)
• persistence (JPA, Repos)
• web (Spring Boot main app)

Use Maven or Gradle to manage dependencies. Modularization improves scalability and testability.

11. How does Spring Boot support virtual threads (Project Loom)?

Answer:
Since Spring Boot 3.2 and Java 21, you can use virtual threads for non-blocking concurrency without complex reactive code.

Enable with:

@Bean
public TaskExecutor taskExecutor() {
 return new SimpleAsyncTaskExecutor(Executors.newVirtualThreadPerTaskExecutor());
}

Virtual threads provide scalability similar to reactive systems but with imperative code style.

Bonus: Behavioral Question

12. Have you worked with Spring Boot in microservices architecture? How did you manage inter-service communication?

Answer:
Yes. I’ve used:

• Spring Cloud OpenFeign for declarative REST clients
• Resilience4j for circuit breakers and retries
• Spring Cloud Config for centralized configuration
• Spring Boot Admin and Actuator for monitoring
• Kafka or RabbitMQ for async messaging

These tools made the system resilient, observable, and easy to manage.

Final Tips for Spring Boot Interviews in 2025