500+ Spring Boot Interview Questions with Answers 2026

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Detailed Exam Domain Coverage

This practice test repository balances production architecture, coding standards, and system security. The distribution maps directly to intermediate and advanced topics you will face in live technical rounds:

• Core Spring Boot (20%): Deconstruct auto-configuration mechanics, custom conditional annotations (@ConditionalOnProperty, @ConditionalOnClass), embedded servlet containers, and complex externalized configuration layouts via multi-profile properties and YAML.

• REST APIs and Microservices (18%): Architect production-grade RESTful services, contract design, HATEOAS, distributed tracing, service discovery mechanisms, and patterns like circuit breakers or API gateways.

• Database and Persistence (15%): Map object-relational models with Spring Data JPA and Hibernate. Deep dive into entity life cycles, relationship mappings, lazy fetching traps, transaction isolation levels, propagation configurations, and performance bottlenecks.

• Security and Authentication (12%): Secure backend services with advanced Spring Security filters. Configure custom authentication providers, implement stateless JWT token architectures, and structure enterprise OAuth2 resource servers.

• Testing and Debugging (10%): Write comprehensive slices with @SpringBootTest, @WebMvcTest, and @DataJpaTest. Master stubbing and mocking with Mockito, structural debugging, localized error handling advice (@RestControllerAdvice), and custom logging profiles.

• Deployment and Monitoring (8%): Leverage Spring Boot Actuator for metrics and live telemetry. Expose secure health check endpoints, configure Prometheus/Grafana integrations, and manage multi-stage Docker builds.

• Best Practices and Design Patterns (7%): Apply design patterns (Factory, Strategy, Proxy) natively inside the IoC container, enforce coding standards, and execute target refactoring steps based on test-driven development.

• Advanced Topics (10%): Address complex enterprise architectures using Spring Cloud components, distributed caching strategies (Redis), asynchronous task execution threads, and multi-service orchestration.

About the Course

Cracking an advanced Java or backend developer interview requires an understanding that goes far beyond simply knowing how to initialize a basic starter project. Modern engineering teams look for professionals who understand exactly what happens under the hood when a Spring application bootstraps, how thread pools handle heavy database transactions, and how to protect microservices from cascading system failures. I designed this 550-question practice test repository specifically to emulate the rigorous, case-study-driven technical questions asked by top tech firms.

Instead of asking you simple vocabulary matching questions, this course presents real-world production challenges: misconfigured spring security filter chains, leaky database connection pools, memory issues with lazy loading, and broken circuit breakers in microservice clusters. Every single question includes a comprehensive, multi-layered technical breakdown. I detail the core logic behind the correct architecture choice while clarifying why the alternatives would degrade application performance or open up security vulnerabilities. If you want to refine your engineering depth, audit your existing Spring framework knowledge, or ensure you pass your upcoming technical screening on your very first try, this question bank provides the realistic practice you need.

Sample Practice Questions Preview

Review these three high-fidelity sample questions to see how the explanations are structured inside this course.

Question 1: Auto-Configuration Diagnostics and Condition Evaluation Outcomes

During the initialization of a complex production application, a custom bean declared inside your configuration class fails to load. You suspect a conflict with a default auto-configuration class. How does Spring Boot process conditional configurations under the hood, and which approach allows you to inspect the decision matrix cleanly?

• A) It uses a single runtime initialization phase where regular beans take precedence over auto-configured beans, allowing you to use a debugger to step through bean factory definitions.

• B) It evaluates @Conditional variants across two clear phases during the application context refresh, and you can inspect the evaluation results via the --debug flag or the Actuator /conditions endpoint.

• C) It processes auto-configuration before reading any user-defined configuration classes, requiring you to manually exclude classes via application property settings.

• D) It uses structural aspect-oriented interception to match configuration files, and you must review the underlying console stack traces to catch bean registration errors.

• E) It executes condition matching via external build-time plugin steps, making it impossible to audit individual bean registration failures dynamically at runtime.

• F) It tracks dependency trees inside an encrypted system file that requires specific administrative access tools to decode during server execution phases.

Correct Answer & Explanation:

• Correct Answer: B

• Why it is correct: Spring Boot uses a two-phase context processing system. It registers explicit user configurations first, followed by auto-configurations. Conditions like @ConditionalOnMissingBean are evaluated dynamically. Running your application with the --debug flag or hitting the Actuator /conditions (or /autoconfig in older versions) endpoint gives you a complete report of why specific auto-configurations matched or failed.

• Why alternative options are incorrect:

  • Option A is incorrect: Setting breakpoints across entire bean definitions is tedious and doesn't reveal the specific evaluation rules used by condition matchers.

  • Option C is incorrect: Auto-configuration runs after user configuration. This timing is what allows your custom beans to override default auto-configured beans.

  • Option D is incorrect: Spring Boot uses standard conditional registration mechanisms rather than complex aspect-oriented programming (AOP) infrastructure to handle configuration profiles.

  • Option E is incorrect: All conditional logic is evaluated dynamically when the application starts, not during compilation or build time.

  • Option F is incorrect: No files are encrypted; the state is managed entirely within the live ApplicationContext memory space.

Question 2: Advanced JPA Transaction Management and Propagation Failure Scenarios

Consider a Spring Boot service method marked with @Transactional(propagation = Propagation.REQUIRED). Inside this method, a secondary local helper method within the same service class is invoked. This helper method is explicitly annotated with @Transactional(propagation = Propagation.REQUIRES_NEW). If the helper method throws a runtime exception, what is the exact outcome regarding the database transaction boundaries?

• A) The helper method spins up a distinct physical database transaction that rolls back independently, leaving the parent transaction unaffected.

• B) The system throws a compiler error because you cannot declare different propagation rules inside the same service layer class.

• C) Spring ignores the REQUIRES_NEW directive because of internal proxy limitations, executing the code inside the parent transaction and rolling back both operations.

• D) The parent transaction instantly commits its current state before passing execution off to the newly created child method transaction block.

• E) The application crashes with a thread deadlock because the database connection pool cannot allocate two connections to the exact same execution thread.

• F) The nested method bypasses the container proxy entirely and writes data directly to the database without any transactional controls.

Correct Answer & Explanation:

• Correct Answer: C

• Why it is correct: Spring uses proxy-based Aspect-Oriented Programming (AOP) by default to manage transactions. When a method calls another method within the same class instance (an intra-class call), the call bypasses the outer proxy wrapper. Consequently, the @Transactional annotation on the helper method is ignored. Both methods execute inside the parent transaction, meaning a runtime exception in the helper method rolls back the entire database interaction.

• Why alternative options are incorrect:

  • Option A is incorrect: Separate transactions would only form if the helper method resided in a separate injected bean, allowing the execution to pass through Spring's proxy framework.

  • Option B is incorrect: Declaring these annotations is valid syntax and will compile without any complaints.

  • Option D is incorrect: REQUIRES_NEW pauses active transactions instead of committing them beforehand. However, that mechanism is never triggered here due to the intra-class call.

  • Option E is incorrect: Deadlocks occur if resources are locked across multiple threads. A single thread running inside a bypassed proxy does not cause a deadlock.

  • Option F is incorrect: The operation doesn't bypass transactional controls entirely; it continues executing under the parent method's active transaction context.

Question 3: Spring Security Filter Chain Customization and Stateful JWT Extraction

You are implementing a stateless API infrastructure protected by JWT authentication tokens. A custom filter extending OncePerRequestFilter is injected into your configuration class. If you register this filter incorrectly using the .addFilterBefore() directive relative to the standard UsernamePasswordAuthenticationFilter, how will the security subsystem react to unauthenticated API requests?

• A) The security subsystem will safely catch the token deficiency during initial compilation, forcing you to adjust the filter ordering.

• B) The application ignores the custom filter completely and routes all traffic directly to public endpoints without validation.

• C) The security layer runs the custom filter first. If token parsing or security context population is skipped, execution falls back to subsequent filters, which reject the request for lacking proper authentication.

• D) The container throws an illegal filter exception on your first request, completely disabling all active web security routing rules.

• E) The server intercepts the request and issues an automatic redirect loop between the login page and your targeted endpoint.

• F) The filter chain breaks completely, allowing any incoming traffic to access protected data without any security checks.

Correct Answer & Explanation:

• Correct Answer: C

• Why it is correct: Custom JWT filters are placed before UsernamePasswordAuthenticationFilter to extract tokens and populate the SecurityContextHolder early. If an incoming request lacks a token, your custom filter should simply call filterChain.doFilter(request, response) to pass the request along. The downstream filters will then see an empty security context and reject the unauthorized request.

• Why alternative options are incorrect:

  • Option A is incorrect: Filter ordering choices are evaluated at runtime, so they will not trigger any build or compilation errors.

  • Option B is incorrect: The system still processes the custom filter; it does not skip it or open up public routing.

  • Option D is incorrect: Registering filters via addFilterBefore is standard practice and will not crash the container runtime.

  • Option E is incorrect: Redirect loops happen with misconfigured form-login systems. They do not happen natively with stateless API endpoints.

  • Option F is incorrect: The filter chain remains intact. If a request skips authentication in your custom filter, subsequent filters like FilterSecurityInterceptor will still catch it and block access.

What to Expect

• Welcome to the Interview Questions Tests to help you prepare for your Spring Boot Interview Questions Practice Test.

• You can retake the exams as many times as you want

• This is a huge original question bank

• You get support from instructors if you have questions

• Each question has a detailed explanation

• Mobile-compatible with the Udemy app

We hope that by now you're convinced! And there are a lot more questions inside the course.