--- title: "Spring Boot Interview Questions (2026): By Level, With Model Answers" url: https://weworkworldwide.com/spring-boot-interview-questions/ description: "Spring Boot interview questions for junior, mid and senior developers — dependency injection, beans, transactions and JPA — with model answers and red flags." date: 2026-07-04T15:36:25+00:00 source: https://weworkworldwide.com/llms.txt --- # Spring Boot Interview Questions (2026): By Level, With Model Answers How to use this Spring Boot does a lot by magic, and candidates who don’t understand that magic get stuck fast. These questions probe how well they know what’s under the auto-configuration. Hiring a Spring Boot developer is easy. Telling a real one from a convincing résumé is the hard part — and it’s most of what we do. These are grouped by level, because the same question that stretches a junior is a warm-up for a senior. ## Junior Spring Boot interview questions 0–2 years Core Spring concepts. ### What is dependency injection and IoC in Spring? What a strong answer covers The container creates and injects dependencies rather than objects creating their own, enabling loose coupling and testability. Red flag News up dependencies instead of injecting them. ### What is a Spring bean? What a strong answer covers An object managed by the Spring container, created and wired according to configuration/annotations. Red flag Cannot say what makes an object a bean. ### What does Spring Boot auto-configuration do? What a strong answer covers Configures sensible defaults based on the classpath and properties, reducing boilerplate. Red flag Thinks it’s magic with no way to override. ### What are the common stereotype annotations? What a strong answer covers `@Component`, `@Service`, `@Repository`, `@Controller` mark beans by role. Red flag Uses them interchangeably with no understanding. ### What is the difference between `@Controller` and `@RestController`? What a strong answer covers `@RestController` combines `@Controller` and `@ResponseBody`, returning data instead of views. Red flag Adds `@ResponseBody` everywhere manually, confused why. ### How does `application.properties`/YAML work? What a strong answer covers Externalised configuration bound to beans, with profiles for per-environment values. Red flag Hardcodes configuration in code. ### What is a REST endpoint mapping? What a strong answer covers `@GetMapping`/`@PostMapping` etc. map HTTP requests to handler methods. Red flag Confuses HTTP verbs and their semantics. ### What is the difference between JAR and WAR deployment? What a strong answer covers Spring Boot favours executable JARs with an embedded server; WARs deploy to an external container. Red flag Assumes an external app server is always required. ## Mid-level Spring Boot interview questions 2–5 years Data, transactions and scopes. ### How do bean scopes work? What a strong answer covers Singleton by default (one per container), plus prototype, request and session scopes; misusing them causes shared-state bugs. Red flag Stores request state in a singleton bean. ### How does `@Transactional` work? What a strong answer covers It wraps a method in a transaction via a proxy; self-invocation bypasses the proxy so the annotation is ignored. Red flag Puts `@Transactional` on a self-called or private method. ### What is Spring Data JPA? What a strong answer covers A repository abstraction generating queries from method names and reducing boilerplate over JPA/Hibernate. Red flag Writes all DAO boilerplate by hand. ### How do you avoid N+1 queries with JPA? What a strong answer covers Fetch joins or entity graphs instead of lazy loading in a loop; be deliberate about fetch types. Red flag Lazy-loads associations in a loop. ### What is the difference between `@Component` scanning and explicit `@Bean`? What a strong answer covers Component scanning auto-detects annotated classes; `@Bean` methods define beans explicitly, useful for third-party classes. Red flag Cannot register a bean for a class it doesn’t own. ### How does exception handling work in Spring MVC? What a strong answer covers `@ExceptionHandler` and `@ControllerAdvice` centralise error handling into consistent responses. Red flag Handles exceptions ad hoc in each controller. ### What is dependency injection by constructor vs field? What a strong answer covers Constructor injection is preferred for immutability, testability and clear required dependencies; field injection hides them. Red flag Uses field injection everywhere. ### How does validation work? What a strong answer covers Bean Validation annotations (`@Valid`, `@NotNull`) validate request bodies automatically. Red flag Validates manually and inconsistently. ## Senior Spring Boot interview questions 5+ years Performance, architecture and reliability. ### How do you profile and tune a Spring Boot service? What a strong answer covers Metrics via Actuator/Micrometer, JVM and GC profiling, connection-pool tuning, and fixing slow queries. Red flag Guesses at bottlenecks without metrics. ### How do you manage transactions across service boundaries? What a strong answer covers Keep transactions local; across services use sagas or the outbox pattern rather than distributed transactions. Red flag Tries to span a DB transaction across microservices. ### How do you design resilient service-to-service calls? What a strong answer covers Timeouts, retries with backoff, circuit breakers (Resilience4j) and bulkheads to contain failures. Red flag Calls downstream services with no timeout. ### How does Spring’s proxy-based AOP affect behaviour? What a strong answer covers Aspects (transactions, caching, security) work via proxies, so self-invocation and final methods can bypass them. Red flag Baffled why `@Cacheable` doesn’t fire on internal calls. ### How do you structure a large Spring Boot application? What a strong answer covers Layered or hexagonal architecture separating web, domain and persistence, with clear module boundaries. Red flag Business logic in controllers, no layering. ### How do you handle configuration and secrets across environments? What a strong answer covers Profiles, externalised config and a secrets manager/vault rather than committed properties. Red flag Commits environment secrets to the repo. ### How do you tune JPA/Hibernate for performance? What a strong answer covers Right fetch strategies, batch sizes, second-level cache where appropriate, DTO projections, and watching generated SQL. Red flag Loads full entity graphs and ignores the SQL. ### How do you make a Spring Boot app observable and production-ready? What a strong answer covers Actuator health/metrics, structured logging, distributed tracing, and readiness/liveness probes. Red flag Ships with no health checks or metrics. **Skip the screening entirely.**We vet Spring Boot engineers so you don’t have to — embed one in your team, or have us build it. [Hire Spring Boot developers](https://weworkworldwide.com/hire-remote-java-developers/)[Compare us](https://weworkworldwide.com/compare/) Build and score a full interview with our free [interview scorecard tool](https://weworkworldwide.com/developer-interview-scorecard/), browse the [full question hub](https://weworkworldwide.com/interview-questions/), or see [how we interview engineers](https://weworkworldwide.com/how-we-interview-engineers/).