Cracking the Spring Boot REST Interview: Tips and Must-Know Questions

Cracking the Spring Boot REST Interview: Tips and Must-Know Questions Work through these 12 questions out loud. Open any question for the full model answer, the trap to avoid, and the follow-up a panel usually asks.

  1. Explain structured concurrency and why it matters.

    In a request handler, open StructuredTaskScope, fork fetchUser and fetchOrders, join both — if orders fail, user fetch cancelled automatically. Safer than manual Future...

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  2. How do Spring Boot Actuator health probes work with Kubernetes?

    Enable probes, configure K8s readinessProbe on /actuator/health/readiness, liveness on /actuator/health/liveness. Custom HealthIndicator for critical deps on readiness group...

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  3. @RestController vs @Controller?

    @Controller is for traditional MVC — return "user/list" view name. @RestController adds @ResponseBody so return types become JSON/XML body — standard for REST APIs. Use...

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  4. What is ProblemDetail (RFC 7807) in Spring 6 error handling?

    @ExceptionHandler(NotFoundException.class) ProblemDetail handle(NotFoundException ex) { return ProblemDetail.forStatusAndDetail(NOT_FOUND, ex.getMessage()); } — consistent 404...

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  5. springdoc-openapi vs legacy springfox — what should new projects use?

    Add springdoc-openapi-starter-webmvc-ui dependency. Annotate with @Operation, @Schema on DTOs. Disable in prod via springdoc.api-docs.enabled=false or secure endpoint. Generate...

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  6. How would you design a rate-limited REST API?

    API gateway or filter applies token bucket per API key — Redis stores tokens with TTL. Exceeding limit returns 429 + Retry-After. Different tiers per plan. Log rejections for...

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  7. How do you handle exceptions globally in Spring?

    Create @RestControllerAdvice with @ExceptionHandler(MethodArgumentNotValidException.class) returning 400 + field map, NotFoundException → 404, generic Exception → 500 without...

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  8. What is the difference between JPA and Hibernate?

    JPA is the API contract; Hibernate is the engine under Spring Boot by default. You write @Entity per JPA spec; Hibernate handles SQL generation. Spring Data JpaRepository adds...

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  9. How does Stream API parallel stream work?

    parallelStream() splits work across common pool threads. Good for CPU-heavy map on large in-memory collections. Bad for small lists, IO inside stream, or ordered stateful...

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  10. How do you test Spring Boot applications?

    Unit test services with Mockito — no Spring. @WebMvcTest + MockMvc for controller contract. @DataJpaTest for repository queries. @SpringBootTest + Testcontainers for critical...

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  11. How do you version REST APIs?

    We use /api/v1/users for clarity. Non-breaking: add optional JSON fields. Breaking: launch v2 path, maintain v1 for 6 months with Deprecation header. Spring maps...

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  12. Explain sealed classes and their purpose in Java 17+.

    sealed interface Shape permits Circle, Rectangle limits who implements Shape. Compiler verifies switch (Shape s) covers all cases — no default needed. Use for domain variants...

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Spring Boot REST Interview Questions and Answers · Top 50 Spring Boot REST Interview Questions and Answers (2026 Edition) · Top 40 Spring Boot REST Interview Questions | Must-Prepare before interview. · Spring Boot REST Interview Questions Every Fresher Must Know

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