Top 50 Spring Boot Interview Questions (2026)
Ranked by how often they come up. Every question has a complete worked answer, runnable code and follow-ups — free to read.
50 questions10 Easy24 Medium9 Tricky7 Hard
- 1
What is Spring Boot?
Easy - 2
Why Spring Boot over Spring Framework?
Medium - 3
Features of Spring Boot.
Easy - 4
Explain @SpringBootApplication.
Medium - 5
Explain Spring Boot startup flow.
Medium - 6
What is SpringApplication.run()?
Easy - 7
Explain embedded Tomcat.
Medium - 8
What are Spring Boot Starters?
Easy - 9
How does Spring Boot reduce boilerplate?
Easy - 10
Explain Spring Boot project structure.
Easy - 11
What is IoC?
Easy - 12
What is Dependency Injection?
Easy - 13
Constructor vs Setter vs Field Injection.
Tricky - 14
Why is Constructor Injection recommended?
Medium - 15
What is ApplicationContext?
Medium - 16
Explain Bean Lifecycle.
Hard - 17
Explain Bean Scopes.
Medium - 18
Difference between @Component, @Service and @Repository.
Medium - 19
Difference between @Primary and @Qualifier.
Tricky - 20
How does Component Scanning work?
Medium - 21
What is Auto Configuration?
Medium - 22
How does @EnableAutoConfiguration work?
Hard - 23
What are Conditional Annotations?
Medium - 24
Explain @ConditionalOnClass.
Medium - 25
Explain @ConditionalOnMissingBean.
Tricky - 26
How is DataSource created automatically?
Medium - 27
How does AutoConfiguration.imports work?
Hard - 28
How do you disable Auto Configuration?
Tricky - 29
What happens when spring-boot-starter-data-jpa is added?
Medium - 30
Explain REST API request flow.
Medium - 31
How does DispatcherServlet work?
Hard - 32
@RestController vs @Controller.
Tricky - 33
@RequestMapping vs @GetMapping.
Tricky - 34
DTO vs Entity.
Medium - 35
Validation using @Valid.
Medium - 36
ResponseEntity.
Medium - 37
Pagination in Spring Boot.
Medium - 38
Sorting in Spring Data.
Medium - 39
What is Spring Data JPA?
Easy - 40
CrudRepository vs JpaRepository.
Medium - 41
Derived Query Methods.
Medium - 42
Lazy Loading vs Eager Loading.
Tricky - 43
Explain N+1 Query Problem.
Medium - 44
Explain @EntityGraph.
Hard - 45
Optimistic Locking.
Tricky - 46
Pessimistic Locking.
Hard - 47
What is Spring Security?
Medium - 48
OAuth2 vs JWT.
Tricky - 49
Authentication vs Authorization.
Easy - 50
How does SecurityFilterChain work?
Hard
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