Schema & Types Interview Questions
Comprehensive schema & types interview questions and answers for Apollo GraphQL. Prepare for your next job interview with expert guidance.
Questions Overview
1. What is Schema Definition Language (SDL) in GraphQL?
Basic2. How do you implement custom scalar types?
Moderate3. What are Unions and Interfaces in GraphQL?
Advanced4. How do you handle schema evolution and versioning?
Advanced5. What are Input Types and their usage?
Basic6. How do you implement schema directives?
Advanced7. What is schema stitching and federation?
Advanced8. How do you handle schema validation?
Moderate9. What are best practices for type design?
Moderate10. How do you implement code generation for types?
Moderate11. What are nullable and non-nullable types?
Basic12. How do you handle schema documentation?
Basic13. What are Enum types and their benefits?
Moderate14. How do you implement type extensions?
Advanced15. What are List types and their handling?
Basic16. How do you implement type resolvers?
Moderate17. What are abstract types and their usage?
Advanced18. How do you handle schema deprecation?
Moderate19. What are schema directives for validation?
Advanced20. How do you implement recursive types?
Advanced1. What is Schema Definition Language (SDL) in GraphQL?
BasicSDL is language for defining GraphQL schemas. Define types, queries, mutations. Features: type system, field definitions, relationships. Essential for API structure definition.
2. How do you implement custom scalar types?
ModerateCustom scalars through scalar type definition, serialization methods. Implement parsing, validation logic. Features: type safety, custom validation. Handle specialized data types.
3. What are Unions and Interfaces in GraphQL?
AdvancedUnions combine multiple types, interfaces define shared fields. Implement type resolution, conditional fields. Features: polymorphic queries, type flexibility. Enable complex type relationships.
4. How do you handle schema evolution and versioning?
AdvancedSchema evolution through careful changes, deprecation notices. Implement backwards compatibility, gradual updates. Features: version management, client compatibility. Maintain API stability.
5. What are Input Types and their usage?
BasicInput types define mutation arguments. Structure complex inputs, validate data. Features: type safety, nested objects. Essential for mutation parameters.
6. How do you implement schema directives?
AdvancedSchema directives modify schema behavior. Implement custom directives, execution logic. Features: field transformation, validation rules. Extend schema capabilities.
7. What is schema stitching and federation?
AdvancedSchema stitching/federation combines multiple schemas. Implement service composition, type merging. Features: distributed schemas, service integration. Enable microservices architecture.
8. How do you handle schema validation?
ModerateSchema validation through tools, linting rules. Implement type checking, consistency rules. Features: schema testing, error detection. Ensure schema quality.
9. What are best practices for type design?
ModerateType design through proper naming, field organization. Implement clear interfaces, proper relationships. Features: schema clarity, maintainability. Follow GraphQL conventions.
10. How do you implement code generation for types?
ModerateCode generation through GraphQL tools, type generators. Generate TypeScript/Flow types. Features: type safety, development efficiency. Automate type definitions.
11. What are nullable and non-nullable types?
BasicType nullability through exclamation mark (!). Define required fields, optional fields. Features: type safety, error prevention. Control field requirements.
12. How do you handle schema documentation?
BasicSchema documentation through descriptions, comments. Implement proper documentation, examples. Features: self-documenting API, tooling support. Improve developer experience.
13. What are Enum types and their benefits?
ModerateEnum types define fixed set of values. Implement type restrictions, validation. Features: type safety, clear constraints. Limit possible field values.
14. How do you implement type extensions?
AdvancedType extensions through extend keyword, additional fields. Modify existing types, add functionality. Features: schema flexibility, modular design. Enable schema evolution.
15. What are List types and their handling?
BasicList types through square brackets notation. Handle array fields, collection types. Features: array validation, null handling. Manage collections of values.
16. How do you implement type resolvers?
ModerateType resolvers through resolver functions, field definitions. Implement data fetching, field computation. Features: data resolution, business logic. Handle field values.
17. What are abstract types and their usage?
AdvancedAbstract types through interfaces, unions. Implement polymorphic schemas, type conditions. Features: type flexibility, shared fields. Enable complex type hierarchies.
18. How do you handle schema deprecation?
ModerateSchema deprecation through @deprecated directive, documentation. Implement migration paths, client communication. Features: version management, backward compatibility. Handle API evolution.
19. What are schema directives for validation?
AdvancedValidation directives through custom implementations. Implement field validation, input constraints. Features: runtime validation, error handling. Ensure data integrity.
20. How do you implement recursive types?
AdvancedRecursive types through self-referential definitions. Implement tree structures, nested data. Features: circular references, depth control. Handle hierarchical data.