What is Apollo Client and its key features?
Apollo Client is a comprehensive state management library for GraphQL. Key features: declarative data fetching, zero-config caching, predictable mutations, automatic query deduplication. Integrates with any GraphQL API and UI framework.
How do you initialize Apollo Client in a React application?
Initialize using ApolloClient constructor, configure with cache and link options. Wrap application with ApolloProvider. Example: new ApolloClient({ cache: new InMemoryCache(), uri: 'graphql-endpoint' }). Set default options for queries/mutations.
What is the InMemoryCache and its importance?
InMemoryCache is Apollo's normalized caching system. Stores query results, handles data normalization. Features: type policies, field policies, custom resolvers. Essential for performance, offline capabilities, data consistency.
How does Apollo Client handle data fetching?
Data fetching through useQuery hook (React), query components. Supports variables, polling, skip/fetchMore. Handles loading/error states automatically. Features automatic caching, real-time updates.
What are the differences between Queries and Mutations?
Queries for reading data (idempotent), Mutations for modifying data. Queries can run parallel, mutations execute sequentially. Queries automatically cached, mutations require cache updates. Different hooks: useQuery vs useMutation.
How does Apollo Client manage local state?
Local state management through field policies, reactive variables. Can extend schema with @client directive. Features: local resolvers, cache manipulation. Integrates with global cache management.
What is the purpose of Apollo Link?
Apollo Link customizes network layer behavior. Chain of middleware for request/response modification. Features: error handling, authentication, logging. Enables advanced network customization.
How does Apollo Client handle errors?
Error handling through GraphQL errors, network errors. Provides error information in query/mutation results. Features: error policies, retry mechanisms. Supports custom error handling logic.
What is the role of TypePolicies in Apollo Client?
TypePolicies configure cache behavior per type. Define key fields, field merging strategies. Features: custom merge functions, field policies. Essential for cache normalization.
How does Apollo Client handle real-time updates?
Real-time updates through subscriptions, polling. WebSocket integration for live data. Features: subscription components/hooks, automatic updates. Supports optimistic UI updates.
What is the purpose of the useQuery hook?
useQuery hook fetches and manages query data. Provides loading/error states, refetch functions. Features: automatic caching, skip/pollInterval options. Essential for React component data fetching.
How do you implement pagination with Apollo Client?
Pagination through fetchMore function, field policies. Supports offset/cursor-based pagination. Features: automatic cache merging, custom merge functions. Handles loading states automatically.
What are Reactive Variables in Apollo Client?
Reactive Variables store local state outside cache. Update components automatically on change. Features: no query requirement, direct reads/writes. Useful for global UI state.
How does Apollo Client handle cache normalization?
Cache normalization through unique identifiers, type policies. Prevents data duplication, ensures consistency. Features: custom key fields, merge functions. Essential for efficient caching.
What is optimistic UI and how to implement it?
Optimistic UI updates cache before server response. Improves perceived performance, user experience. Features: optimistic response object, error rollback. Used with mutations for instant feedback.
How do you handle authentication in Apollo Client?
Authentication through HTTP headers, context. Configure ApolloLink for token management. Features: token refresh, error handling. Supports different auth strategies.
What are Fragment components and their use?
Fragments define reusable field sets. Promote code reuse, maintainability. Features: colocated queries, type safety. Used for component-specific data requirements.
How does Apollo Client handle query deduplication?
Query deduplication combines identical concurrent requests. Reduces network traffic, improves performance. Features: automatic caching, request batching. Configurable through client options.
What is the purpose of cache redirects?
Cache redirects customize cache reading behavior. Define relationships between cached entities. Features: field policies, custom resolvers. Useful for complex data relationships.
How do you handle file uploads in Apollo Client?
File uploads through apollo-upload-client package. Supports multipart form data, progress tracking. Features: multiple file uploads, abort capability. Requires server-side configuration.
What are the best practices for error handling?
Error handling through error policies, custom error handling. Implement retry logic, user feedback. Features: error components, global error handling. Consider different error types.
How does Apollo Client handle offline support?
Offline support through cache persistence, local state. Implement retry strategies, queue mutations. Features: cache storage, conflict resolution. Consider offline-first architecture.
What is the purpose of fetchPolicy?
FetchPolicy controls cache/network behavior. Options: cache-first, network-only, etc. Features: customizable per query, default policies. Balances performance and data freshness.
How do you implement code splitting with Apollo Client?
Code splitting through dynamic imports, lazy components. Supports query splitting, fragment colocation. Features: automatic chunk loading, performance optimization. Important for large applications.
What is the role of field policies?
Field policies customize field behavior in cache. Define read/write functions, merge strategies. Features: custom field handling, computed fields. Essential for complex cache management.
How do you handle data prefetching?
Data prefetching through query preloading, cache priming. Improves perceived performance, user experience. Features: manual prefetch, automatic preloading. Consider resource utilization.
What are the common performance optimization techniques?
Performance optimization through caching, query batching. Implement field limiting, pagination. Features: automatic garbage collection, cache policies. Consider bundle size, network usage.
How do you implement client-side search/filtering?
Client-side operations through local state, field policies. Implement search logic, filtering functions. Features: reactive variables, local resolvers. Consider performance implications.
What is the purpose of @client directive?
Client directive marks fields for local-only operations. Enables client-side resolvers, computed fields. Features: local state management, schema extension. Used for UI state, computed data.
How do you handle server-side rendering (SSR)?
SSR through getDataFromTree, cache extraction. Handle initial state, hydration. Features: automatic cache population, state transfer. Consider SEO, performance requirements.
How do you implement dynamic queries in Apollo Client?
Dynamic queries using query variables, conditional fields. Implement skip/include directives. Features: runtime variables, dynamic field selection. Consider query complexity, caching implications.
What are the different query loading states?
Loading states: loading, error, data, networkStatus. Access through useQuery hook result. Features: partial data handling, refetch status. Important for user feedback, error handling.
How do you handle query variables effectively?
Query variables through useQuery options, variable definitions. Support default values, type safety. Features: variable validation, dynamic updates. Consider variable scoping, reusability.
What are the available fetchPolicy options?
FetchPolicies: cache-first, network-only, cache-and-network, no-cache, standby. Control cache/network behavior. Features: per-query configuration, default policies. Balance performance and data freshness.
How do you implement query polling?
Polling through pollInterval option in useQuery. Configure interval timing, automatic updates. Features: start/stop polling, skip conditions. Consider server load, real-time requirements.
What is the purpose of notifyOnNetworkStatusChange?
NotifyOnNetworkStatusChange tracks detailed network status. Provides component updates for network changes. Features: refetch status, error states. Important for loading indicators, error handling.
How do you handle query errors effectively?
Error handling through errorPolicy option, error results. Implement error boundaries, retry logic. Features: partial data handling, error recovery. Consider user experience, error reporting.
What are query refetching strategies?
Refetching through refetch function, network-only policy. Support manual/automatic triggers, variables update. Features: selective refetching, loading states. Consider cache invalidation, performance.
How do you implement skip and include directives?
Skip/Include directives for conditional field inclusion. Control field selection at runtime. Features: dynamic queries, conditional data. Consider query complexity, performance impact.
What is the purpose of standby fetchPolicy?
Standby policy pauses query execution. Useful for inactive queries, resource management. Features: manual execution control, cache preservation. Consider memory usage, query prioritization.
How do you handle partial query responses?
Partial responses through errorPolicy: 'all'. Handle missing fields, null values. Features: partial data rendering, error boundaries. Consider user experience, data completeness.
What is query batching and its implementation?
Query batching combines multiple queries into single request. Implement through Apollo Link batch. Features: automatic batching, timeout configuration. Consider network optimization, request timing.
How do you implement query retry logic?
Retry logic through retry link configuration. Handle network errors, timeout scenarios. Features: exponential backoff, max attempts. Consider error types, retry conditions.
What are the best practices for query organization?
Organization through query separation, fragments. Implement colocated queries, reusable parts. Features: maintainable structure, type safety. Consider code reuse, maintainability.
How do you handle query timeouts?
Timeouts through Apollo Link configuration. Implement timeout logic, error handling. Features: custom timeout values, cancel operations. Consider network conditions, user experience.
What is query deduplication and its benefits?
Deduplication combines identical concurrent requests. Reduces network traffic, improves performance. Features: automatic caching, request optimization. Consider cache policies, timing.
How do you implement query prefetching?
Prefetching through client.query, preloadQuery. Improve perceived performance, data availability. Features: cache warming, anticipatory loading. Consider resource usage, timing.
What are the strategies for query performance optimization?
Optimization through field selection, pagination. Implement proper caching, batching. Features: minimal queries, efficient loading. Consider data requirements, network usage.
How do you handle nested queries effectively?
Nested queries through proper field selection, fragments. Implement efficient data loading, caching. Features: normalized data, relationship handling. Consider query complexity, performance.
What is the purpose of query signatures?
Query signatures uniquely identify operations. Used for caching, deduplication. Features: automatic generation, query identification. Consider cache keys, operation tracking.
How do you implement query cancellation?
Cancellation through AbortController, cleanup functions. Handle component unmount, user actions. Features: request termination, resource cleanup. Consider in-flight requests, state management.
What are query directives and their usage?
Directives modify query execution behavior. Implement @skip, @include, custom directives. Features: conditional fields, runtime control. Consider schema support, client capabilities.
How do you handle query variables typescript?
TypeScript support through codegen, type definitions. Implement type safety, variable validation. Features: automatic types, compile-time checks. Consider development experience, maintenance.
What is the role of query context?
Context provides global query configuration. Share data between resolvers, links. Features: auth tokens, headers management. Consider request lifecycle, security implications.
How do you implement query persistence?
Persistence through cache storage, local state. Implement offline support, data retention. Features: cache serialization, state recovery. Consider storage limits, data privacy.
What are the strategies for query error recovery?
Error recovery through retry logic, fallback data. Implement error boundaries, user feedback. Features: graceful degradation, recovery options. Consider user experience, data integrity.
How do you handle query authorization?
Authorization through context, directives. Implement access control, role checks. Features: permission handling, secure queries. Consider security requirements, user roles.
What is query cost analysis?
Cost analysis evaluates query complexity, resource usage. Implement limits, optimization suggestions. Features: query validation, performance metrics. Consider server resources, scalability.
How do you implement query monitoring?
Monitoring through Apollo Studio, custom metrics. Track performance, errors, usage patterns. Features: analytics, debugging tools. Consider monitoring strategy, performance impact.
What are the best practices for query testing?
Testing through mock providers, test utilities. Implement unit tests, integration tests. Features: query mocking, response simulation. Consider test coverage, maintenance.
How does Apollo Client's cache normalization work?
Cache normalization flattens nested data using unique identifiers. Implements automatic ID generation, reference handling. Features: customizable key fields, type policies. Essential for consistent data representation and updates.
What are Type Policies and their importance?
Type policies define how types are stored and retrieved from cache. Configure key fields, field behaviors. Features: custom merge functions, field read/write functions. Controls cache behavior per GraphQL type.
How do you implement local state management?
Local state through reactive variables, local-only fields. Implement client-side resolvers, type extensions. Features: @client directive, local mutations. Manages UI state alongside server data.
What are Field Policies and their usage?
Field policies customize individual field behavior. Define read/write functions, merge strategies. Features: computed fields, custom caching logic. Handles complex field requirements.
How do you handle cache updates after mutations?
Cache updates through update functions, refetchQueries. Implement optimistic updates, cache modifications. Features: automatic updates, manual cache writes. Ensures cache consistency after mutations.
What is cache persistence and how to implement it?
Cache persistence stores cache data locally. Uses apollo3-cache-persist. Features: automatic persistence, custom storage. Enables offline support, faster initial loads.
How do you handle cache eviction and garbage collection?
Cache eviction through evict method, garbage collection. Implement cache cleanup, reference management. Features: automatic garbage collection, manual eviction. Manages cache size and memory usage.
What are cache redirects and their usage?
Cache redirects customize cache data access. Define field reading behavior, data relationships. Features: custom resolvers, field policies. Handles complex data relationships and queries.
How do you implement optimistic responses?
Optimistic responses update UI before server response. Implement temporary cache updates, rollback handling. Features: immediate feedback, error recovery. Improves perceived performance.
What is cache initialization and its importance?
Cache initialization sets up initial cache state. Configure type policies, initial data. Features: preloaded state, type configuration. Essential for proper cache setup and behavior.
How do you handle pagination in cache?
Pagination through field policies, merge functions. Implement cursor-based/offset pagination. Features: automatic merging, custom merge strategies. Manages paginated data in cache.
What are reactive variables?
Reactive variables manage local state. Independent of GraphQL operations. Features: direct reads/writes, automatic updates. Simplifies local state management.
How do you implement cache invalidation?
Cache invalidation through evict, modify methods. Implement selective updates, refetching. Features: field-level invalidation, type-level eviction. Ensures data freshness.
What are cache policies and their types?
Cache policies control data reading/writing. Types: cache-first, network-only, etc. Features: customizable per query, default settings. Balances performance and data freshness.
How do you handle cache conflicts?
Cache conflicts through merge functions, conflict resolution. Implement custom merging logic, update priorities. Features: deterministic merging, conflict detection. Maintains cache consistency.
What is cache extraction and its usage?
Cache extraction retrieves current cache state. Used for SSR, persistence. Features: serialization, state transfer. Important for server rendering, cache backup.
How do you implement cache debugging?
Cache debugging through Apollo DevTools, logging. Inspect cache state, watch updates. Features: cache explorer, update tracking. Essential for development and troubleshooting.
What are custom resolvers in cache?
Custom resolvers handle field computation, data transformation. Implement local-only fields, computed values. Features: field-level resolution, cache integration. Extends cache capabilities.
How do you handle real-time updates in cache?
Real-time updates through subscriptions, cache updates. Implement automatic merging, optimistic UI. Features: subscription integration, cache consistency. Maintains real-time data state.
What is cache pruning and its importance?
Cache pruning removes unused data. Implements automatic cleanup, reference tracking. Features: memory optimization, cache size management. Prevents cache bloat.
How do you handle cache updates in lists?
List updates through field policies, merge functions. Implement array operations, item updates. Features: automatic merging, custom ordering. Manages list-based data.
What are cache hints and their usage?
Cache hints provide caching instructions. Configure max-age, scope. Features: field-level control, cache behavior. Optimizes cache performance and freshness.
How do you implement cache preloading?
Cache preloading through initial state, prefetching. Implement data warming, startup data. Features: performance optimization, initial load. Improves application startup.
What is cache manipulation and its methods?
Cache manipulation through writeQuery, writeFragment. Implement direct updates, data modifications. Features: programmatic updates, cache control. Enables manual cache management.
How do you handle cache fragmentation?
Cache fragmentation through proper normalization, cleanup. Implement reference management, garbage collection. Features: performance optimization, memory management. Maintains cache efficiency.
What are cache redirects and their implementation?
Cache redirects customize data access paths. Implement field policies, custom resolvers. Features: data relationship handling, query optimization. Manages complex data access patterns.
How do you implement cache persistence strategies?
Persistence strategies through storage options, update policies. Implement persistence plugins, recovery logic. Features: offline support, state preservation. Ensures data availability.
What are cache policies for nested objects?
Nested object policies through type policies, merge functions. Implement relationship handling, nested updates. Features: complex data structures, reference management. Handles nested data effectively.
How do you implement cache warming?
Cache warming through prefetching, initial data. Implement strategic loading, data preparation. Features: performance optimization, user experience. Improves application responsiveness.
What are best practices for cache management?
Best practices include proper normalization, type policies, field policies. Implement efficient updates, proper cleanup. Features: performance optimization, maintainability. Ensures robust cache implementation.
How do you implement mutations in Apollo Client?
Mutations implemented using useMutation hook. Configure variables, options, cache updates. Features: optimistic updates, error handling. Common pattern: mutation function returns promise with result.
What are optimistic updates and their implementation?
Optimistic updates provide immediate UI feedback before server response. Implement through optimisticResponse option. Features: temporary cache updates, automatic rollback on error. Improves perceived performance.
How do you handle cache updates after mutations?
Cache updates through update function, refetchQueries. Implement cache modifications, field updates. Features: automatic cache normalization, manual cache writes. Ensures cache consistency.
What is the purpose of refetchQueries?
RefetchQueries updates queries after mutation. Specify queries to refetch, variables. Features: automatic query updates, cache refresh. Ensures data consistency across components.
How do you implement error handling in mutations?
Error handling through onError callback, error policies. Implement error messages, recovery logic. Features: error tracking, user feedback. Handles network errors, GraphQL errors.
What are mutation variables and their usage?
Mutation variables pass dynamic data to mutations. Configure through options object, typed variables. Features: type safety, dynamic values. Handles user input, dynamic data.
How do you handle concurrent mutations?
Concurrent mutations through mutation queue, synchronization. Implement ordering, dependency handling. Features: race condition prevention, sequence control. Maintains data consistency.
What is update function in mutations?
Update function modifies cache after mutation. Access cache directly, perform updates. Features: manual cache writes, complex updates. Handles custom cache modifications.
How do you implement batch mutations?
Batch mutations combine multiple operations. Implement through Apollo Link batch. Features: request batching, optimization. Reduces network requests, improves performance.
What are mutation loading states?
Loading states track mutation progress. Access through mutation result object. Features: loading indicator, disabled states. Handles user feedback, UI updates.
How do you handle mutation rollbacks?
Rollbacks through error handling, cache restoration. Implement recovery logic, state management. Features: automatic rollback, manual recovery. Handles failed mutations.
What are mutation hooks and their benefits?
Mutation hooks provide declarative mutation handling. Access mutation function, result data. Features: React integration, type safety. Simplifies mutation implementation.
How do you implement file uploads in mutations?
File uploads through Apollo Upload Client. Handle multipart form data, progress. Features: file handling, upload tracking. Supports single/multiple file uploads.
What are mutation options and configurations?
Mutation options configure behavior. Include variables, update function, optimistic response. Features: error policies, refetch queries. Controls mutation execution.
How do you handle dependent mutations?
Dependent mutations through chaining, async/await. Implement sequence control, error handling. Features: mutation ordering, data dependencies. Manages related mutations.
What are mutation result types?
Result types define mutation responses. Include data, loading state, error information. Features: type safety, result handling. Structures mutation responses.
How do you implement offline mutations?
Offline mutations through queue system, persistence. Implement retry logic, conflict resolution. Features: offline support, sync handling. Handles network interruptions.
What is mutation completion handling?
Completion handling through onCompleted callback. Implement success actions, notifications. Features: result processing, UI updates. Handles successful mutations.
How do you handle mutation side effects?
Side effects through update function, callbacks. Implement additional actions, state updates. Features: cache modifications, external updates. Manages mutation impacts.
What are mutation policies?
Mutation policies control execution behavior. Configure error handling, cache updates. Features: retry policies, update strategies. Defines mutation behavior.
How do you implement mutation testing?
Mutation testing through mock providers, test utilities. Implement assertions, response mocking. Features: result verification, error testing. Ensures mutation reliability.
What are mutation fragments?
Mutation fragments define reusable mutation parts. Share common fields, type definitions. Features: code reuse, maintainability. Reduces duplicate mutation code.
How do you handle mutation conflicts?
Conflict handling through version checks, merge strategies. Implement conflict resolution, retry logic. Features: data consistency, user feedback. Manages concurrent updates.
What are mutation directives?
Mutation directives modify mutation behavior. Configure execution, caching. Features: custom directives, behavior control. Extends mutation capabilities.
How do you implement mutation rate limiting?
Rate limiting through Apollo Link, request throttling. Implement request control, queue management. Features: request limits, timing control. Prevents server overload.
What are mutation best practices?
Best practices include proper error handling, optimistic updates, cache management. Implement type safety, testing. Features: performance optimization, reliability. Ensures robust mutations.
How do you handle mutation authorization?
Authorization through context, headers. Implement access control, token handling. Features: permission checks, secure mutations. Ensures authorized access.
What is mutation composition?
Composition combines multiple mutations. Implement reusable parts, shared logic. Features: code organization, maintainability. Structures complex mutations.
How do you implement mutation monitoring?
Monitoring through Apollo Studio, custom tracking. Implement performance metrics, error logging. Features: analytics, debugging. Tracks mutation behavior.
How do you set up testing environment for Apollo Client?
Setup using @testing-library/react, MockedProvider. Configure test wrappers, mock responses. Features: mock Apollo Client, query mocking. Essential for unit and integration testing.
What is MockedProvider and its usage?
MockedProvider enables Apollo Client testing. Provides mock responses, error simulation. Features: request matching, response timing control. Essential for component testing.
How do you test queries in Apollo Client?
Query testing through mock responses, assertion utilities. Test loading states, error handling. Features: response timing, cache behavior. Verify data fetching logic.
What are the strategies for testing mutations?
Mutation testing through mock functions, result verification. Test optimistic updates, error scenarios. Features: cache updates, response handling. Verify data modification logic.
How do you debug Apollo Client cache?
Cache debugging through Apollo DevTools, cache inspection. Monitor cache updates, state changes. Features: cache explorer, query watcher. Essential for troubleshooting.
What are testing patterns for error scenarios?
Error testing through mock errors, response simulation. Test error handling, recovery logic. Features: network errors, GraphQL errors. Verify error handling implementation.
How do you implement integration testing?
Integration testing through test utilities, component rendering. Test component interactions, data flow. Features: full rendering, async testing. Verify component integration.
What tools are available for Apollo debugging?
Debugging tools: Apollo DevTools, React DevTools, Network inspector. Monitor queries, cache state, performance. Features: request tracking, state inspection. Essential for development.
How do you test cache policies?
Cache policy testing through mock operations, state verification. Test cache behavior, updates. Features: field policies, type policies. Verify cache configuration.
What are mocking best practices?
Mocking practices: realistic data, proper typing. Implement consistent mocks, error cases. Features: type generation, schema validation. Ensure reliable test data.
How do you test optimistic responses?
Optimistic response testing through update verification, timing checks. Test UI updates, rollbacks. Features: cache inspection, state tracking. Verify optimistic behavior.
What is snapshot testing in Apollo?
Snapshot testing captures component output. Compare rendered content, query results. Features: automated comparison, update mechanism. Verify rendering consistency.
How do you debug network requests?
Network debugging through request inspection, response analysis. Monitor headers, payload data. Features: request tracking, error detection. Verify API communication.
What are testing strategies for subscriptions?
Subscription testing through mock WebSocket, event simulation. Test real-time updates, connection handling. Features: subscription mocking, event verification. Verify real-time behavior.
How do you implement performance testing?
Performance testing through metrics collection, timing analysis. Test query execution, cache efficiency. Features: performance tracking, optimization verification. Verify system performance.
What are debugging techniques for cache inconsistencies?
Cache debugging through state inspection, update tracking. Identify inconsistencies, normalization issues. Features: cache comparison, update verification. Resolve cache problems.
How do you test local state management?
Local state testing through resolver verification, cache inspection. Test field policies, local mutations. Features: state management, update validation. Verify local operations.
What are error boundary testing patterns?
Error boundary testing through error simulation, recovery verification. Test fallback UI, error handling. Features: error capture, component recovery. Verify error management.
How do you debug query variables?
Variable debugging through request inspection, value tracking. Monitor variable usage, type validation. Features: variable inspection, value verification. Resolve query issues.
What are testing utilities in Apollo Client?
Testing utilities include MockedProvider, test renderers. Provide mock data, assertion helpers. Features: component testing, query simulation. Essential for test implementation.
How do you implement end-to-end testing?
E2E testing through Cypress, TestCafe integration. Test full application flow, user scenarios. Features: full stack testing, integration verification. Verify system functionality.
What are debugging strategies for mutations?
Mutation debugging through update tracking, result verification. Monitor cache changes, optimistic updates. Features: mutation tracking, state verification. Resolve update issues.
How do you test pagination implementation?
Pagination testing through data loading verification, cache updates. Test fetch more functionality, cursor handling. Features: load testing, cache behavior. Verify pagination logic.
What are common testing pitfalls?
Common pitfalls: improper mocking, async handling issues. Address timing problems, cache management. Features: test isolation, proper setup. Avoid testing antipatterns.
How do you debug fragment usage?
Fragment debugging through composition analysis, reuse verification. Monitor fragment spreading, type conditions. Features: fragment inspection, usage tracking. Resolve fragment issues.
What are testing patterns for error handling?
Error handling testing through scenario simulation, recovery verification. Test error states, user feedback. Features: error testing, handling validation. Verify error management.
How do you implement mock schema?
Mock schema through type definitions, resolvers. Implement test data, response patterns. Features: schema simulation, type checking. Essential for isolated testing.
What are debugging tools for cache policies?
Cache policy debugging through policy inspection, behavior analysis. Monitor field policies, type policies. Features: policy tracking, update verification. Resolve policy issues.
How do you test reactive variables?
Reactive variable testing through value tracking, update verification. Test reactivity, dependency updates. Features: state management, update validation. Verify reactive behavior.
What are best practices for component testing?
Component testing practices: isolation, proper mocking. Implement realistic scenarios, error cases. Features: component rendering, interaction testing. Ensure reliable tests.
How do you implement authentication in Apollo Client?
Authentication through HTTP headers, context setup. Use Apollo Link for token management. Features: JWT handling, session management. Implement token refresh, secure storage.
What are the best practices for token management?
Token management through secure storage, automatic refresh. Implement token rotation, expiration handling. Features: JWT validation, secure transmission. Consider security implications.
How do you handle authorization in queries and mutations?
Authorization through directives, field-level checks. Implement role-based access, permission validation. Features: context-based auth, error handling. Ensure proper access control.
What is the role of Apollo Link in security?
Apollo Link manages request/response pipeline. Add authentication headers, handle errors. Features: token injection, request modification. Essential for security implementation.
How do you implement secure file uploads?
Secure uploads through proper validation, token verification. Implement file type checks, size limits. Features: multipart requests, progress tracking. Consider security measures.
What are security considerations for cache?
Cache security through proper data handling, sensitive info protection. Implement cache policies, access control. Features: data encryption, secure storage. Prevent data leaks.
How do you handle OAuth integration?
OAuth integration through proper flow implementation, token management. Handle authorization code, access tokens. Features: refresh flow, state management. Ensure secure authentication.
What are CORS considerations in Apollo Client?
CORS handling through proper server configuration, client setup. Implement request headers, preflight handling. Features: origin validation, credential handling. Ensure secure cross-origin requests.
How do you implement role-based access control?
RBAC through directives, context checks. Implement permission system, role validation. Features: hierarchical roles, permission inheritance. Ensure proper authorization.
What are security best practices for mutations?
Mutation security through proper validation, authorization checks. Implement input sanitization, access control. Features: data validation, error handling. Prevent unauthorized modifications.
How do you handle session management?
Session management through proper storage, expiration handling. Implement session tokens, refresh mechanism. Features: session validation, secure storage. Ensure secure user sessions.
What are security implications of persisted queries?
Persisted queries security through proper whitelisting, validation. Implement query registry, access control. Features: query verification, cache security. Prevent query injection.
How do you implement secure websocket connections?
Secure websockets through proper authentication, token validation. Implement connection params, protocol security. Features: connection lifecycle, error handling. Ensure secure real-time communication.
What are security considerations for error handling?
Error security through proper message handling, stack trace protection. Implement error masking, logging strategy. Features: error sanitization, security logging. Prevent sensitive information exposure.
How do you implement rate limiting?
Rate limiting through proper configuration, request tracking. Implement throttling logic, error responses. Features: limit enforcement, user identification. Prevent abuse and DOS attacks.
What are security best practices for local state?
Local state security through proper encryption, access control. Implement secure storage, data handling. Features: sensitive data protection, secure operations. Prevent client-side vulnerabilities.
How do you handle secure data persistence?
Secure persistence through proper encryption, storage strategy. Implement secure cache, local storage. Features: data protection, access control. Ensure secure client-side storage.
What are security considerations for fragments?
Fragment security through proper access control, type checking. Implement fragment masking, permission validation. Features: field-level security, type restrictions. Prevent unauthorized data access.
How do you implement secure file downloads?
Secure downloads through proper authentication, access validation. Implement token verification, stream handling. Features: file access control, secure transfer. Ensure secure file delivery.
What are security implications of client directives?
Directive security through proper validation, execution control. Implement directive restrictions, permission checks. Features: directive scope, security boundaries. Prevent directive misuse.
What is Schema Definition Language (SDL) in GraphQL?
SDL is language for defining GraphQL schemas. Define types, queries, mutations. Features: type system, field definitions, relationships. Essential for API structure definition.
How do you implement custom scalar types?
Custom scalars through scalar type definition, serialization methods. Implement parsing, validation logic. Features: type safety, custom validation. Handle specialized data types.
What are Unions and Interfaces in GraphQL?
Unions combine multiple types, interfaces define shared fields. Implement type resolution, conditional fields. Features: polymorphic queries, type flexibility. Enable complex type relationships.
How do you handle schema evolution and versioning?
Schema evolution through careful changes, deprecation notices. Implement backwards compatibility, gradual updates. Features: version management, client compatibility. Maintain API stability.
What are Input Types and their usage?
Input types define mutation arguments. Structure complex inputs, validate data. Features: type safety, nested objects. Essential for mutation parameters.
How do you implement schema directives?
Schema directives modify schema behavior. Implement custom directives, execution logic. Features: field transformation, validation rules. Extend schema capabilities.
What is schema stitching and federation?
Schema stitching/federation combines multiple schemas. Implement service composition, type merging. Features: distributed schemas, service integration. Enable microservices architecture.
How do you handle schema validation?
Schema validation through tools, linting rules. Implement type checking, consistency rules. Features: schema testing, error detection. Ensure schema quality.
What are best practices for type design?
Type design through proper naming, field organization. Implement clear interfaces, proper relationships. Features: schema clarity, maintainability. Follow GraphQL conventions.
How do you implement code generation for types?
Code generation through GraphQL tools, type generators. Generate TypeScript/Flow types. Features: type safety, development efficiency. Automate type definitions.
What are nullable and non-nullable types?
Type nullability through exclamation mark (!). Define required fields, optional fields. Features: type safety, error prevention. Control field requirements.
How do you handle schema documentation?
Schema documentation through descriptions, comments. Implement proper documentation, examples. Features: self-documenting API, tooling support. Improve developer experience.
What are Enum types and their benefits?
Enum types define fixed set of values. Implement type restrictions, validation. Features: type safety, clear constraints. Limit possible field values.
How do you implement type extensions?
Type extensions through extend keyword, additional fields. Modify existing types, add functionality. Features: schema flexibility, modular design. Enable schema evolution.
What are List types and their handling?
List types through square brackets notation. Handle array fields, collection types. Features: array validation, null handling. Manage collections of values.
How do you implement type resolvers?
Type resolvers through resolver functions, field definitions. Implement data fetching, field computation. Features: data resolution, business logic. Handle field values.
What are abstract types and their usage?
Abstract types through interfaces, unions. Implement polymorphic schemas, type conditions. Features: type flexibility, shared fields. Enable complex type hierarchies.
How do you handle schema deprecation?
Schema deprecation through @deprecated directive, documentation. Implement migration paths, client communication. Features: version management, backward compatibility. Handle API evolution.
What are schema directives for validation?
Validation directives through custom implementations. Implement field validation, input constraints. Features: runtime validation, error handling. Ensure data integrity.
How do you implement recursive types?
Recursive types through self-referential definitions. Implement tree structures, nested data. Features: circular references, depth control. Handle hierarchical data.
What are GraphQL Subscriptions and their purpose?
Subscriptions enable real-time data updates through WebSocket connection. Maintain live connection for event-based updates. Features: real-time data, event handling. Essential for live updates.
How do you implement WebSocket setup for subscriptions?
WebSocket setup through split network interface, protocol configuration. Configure connection parameters, authentication. Features: persistent connection, protocol handling. Enable real-time communication.
What is the role of subscription client?
Subscription client manages WebSocket connections, subscription lifecycle. Handle connection states, message processing. Features: message queuing, reconnection logic. Manage subscription operations.
How do you handle subscription authentication?
Subscription authentication through connection params, token validation. Implement secure WebSocket connection, session management. Features: token handling, connection security. Ensure secure subscriptions.
What are subscription events and their handling?
Subscription events through PubSub system, event filtering. Implement event triggers, data transformation. Features: event publishing, subscription filtering. Handle real-time updates.
How do you implement subscription cleanup?
Subscription cleanup through proper unsubscription, connection termination. Handle component unmount, cleanup effects. Features: resource management, memory cleanup. Prevent memory leaks.
What are subscription variables?
Subscription variables through dynamic parameters, event filtering. Configure subscription behavior, data filtering. Features: dynamic subscriptions, parameter handling. Customize subscription data.
How do you handle subscription errors?
Subscription errors through error callbacks, connection recovery. Implement error handling, retry logic. Features: error reporting, connection management. Handle subscription failures.
What are subscription link options?
Subscription link options through configuration parameters, connection settings. Configure timeout, reconnect attempts. Features: link customization, behavior control. Optimize subscription handling.
How do you implement subscription filtering?
Subscription filtering through withFilter function, filter conditions. Implement data filtering, event selection. Features: selective updates, data relevance. Control update flow.
What is subscription payload transformation?
Payload transformation through resolvers, data mapping. Implement data formatting, structure conversion. Features: data shaping, response formatting. Customize subscription data.
How do you handle subscription reconnection?
Reconnection handling through retry policies, connection monitoring. Implement backoff strategy, state recovery. Features: connection resilience, session management. Maintain subscription stability.
What are subscription contexts?
Subscription contexts through context providers, data sharing. Share data across subscription resolvers. Features: context access, data availability. Enable shared subscription state.
How do you implement subscription testing?
Subscription testing through mock WebSocket, event simulation. Test subscription behavior, event handling. Features: connection testing, event verification. Ensure subscription reliability.
What are subscription best practices?
Best practices include proper cleanup, error handling, connection management. Implement efficient filtering, payload optimization. Features: performance consideration, resource management. Optimize subscription usage.
What are different types of errors in Apollo GraphQL?
Error types include: Network errors, GraphQL errors, Runtime errors. Network errors for connection issues, GraphQL errors for operation failures, Runtime errors for execution problems. Each requires specific handling strategies.
How do you implement global error handling?
Global error handling through error link, onError callback. Implement centralized error processing, logging. Features: error transformation, retry logic. Handle application-wide errors.
What are error policies in Apollo Client?
Error policies control how errors affect result data. Options: none, all, ignore. Determine partial data handling, error inclusion. Configure per-operation behavior.
How do you handle network errors?
Network error handling through retry logic, fallback strategies. Implement timeout handling, offline detection. Features: connection recovery, user feedback. Manage connectivity issues.
What is error tracking and monitoring?
Error tracking through logging services, monitoring tools. Implement error reporting, analytics collection. Features: error patterns, performance impact. Monitor application health.
How do you implement mutation error handling?
Mutation error handling through try-catch blocks, error callbacks. Handle operation failures, optimistic updates. Features: rollback logic, error recovery. Manage mutation failures.
What are error links in Apollo Client?
Error links provide custom error handling middleware. Intercept and process errors, modify error behavior. Features: error transformation, retry logic. Extend error handling capabilities.
How do you handle partial errors?
Partial error handling through error policies, data extraction. Process partial responses, handle missing data. Features: graceful degradation, fallback content. Manage incomplete results.
What is error UI implementation?
Error UI through error boundaries, component feedback. Display error messages, recovery options. Features: user communication, action guidance. Improve error experience.
How do you implement retry logic?
Retry logic through retry link, attempt configuration. Implement exponential backoff, max attempts. Features: retry conditions, timeout handling. Manage operation retries.
What are error transformations?
Error transformations through custom error processing, formatting. Modify error structure, add context. Features: error normalization, message formatting. Standardize error handling.
How do you handle subscription errors?
Subscription error handling through connection monitoring, error callbacks. Handle WebSocket errors, connection failures. Features: reconnection logic, state recovery. Manage subscription issues.
What are error boundaries in React Apollo?
Error boundaries catch rendering errors, provide fallback UI. Implement component-level error handling. Features: error isolation, recovery options. Prevent application crashes.
How do you implement error logging?
Error logging through centralized service, structured formats. Implement error categorization, context capture. Features: log aggregation, analysis tools. Track application errors.
What are error recovery strategies?
Recovery strategies through fallback options, state reset. Implement data recovery, cache updates. Features: graceful degradation, user feedback. Handle error recovery.
How do you initialize Apollo Client?
Initialize through ApolloClient constructor, configuration options. Set up cache, link configuration. Features: network interface, cache setup. Essential for client creation.
What are the essential Apollo Client options?
Essential options include: uri for GraphQL endpoint, cache implementation, default options. Configure link chain, error handling. Features: request policies, connection settings.
How do you configure cache settings?
Cache configuration through InMemoryCache options, type policies. Set up field policies, cache behavior. Features: normalization settings, custom identifiers.
What is Apollo Link and its configuration?
Apollo Link configures request pipeline, middleware chain. Set up network handling, error processing. Features: request modification, response handling.
How do you set up authentication?
Authentication setup through context, headers configuration. Implement token management, auth middleware. Features: request authorization, session handling.
What is local state configuration?
Local state through cache configuration, local resolvers. Set up client-side fields, local mutations. Features: local data management, cache integration.
How do you configure error handling?
Error handling through onError link, global handlers. Set up error policies, retry logic. Features: error transformation, recovery strategies.
What are fetch policies and their configuration?
Fetch policies control cache/network behavior. Configure default policies, per-query settings. Features: cache usage, network requests.
How do you set up subscriptions?
Subscription setup through WebSocket link, protocol configuration. Configure connection parameters, client options. Features: real-time updates, connection management.
What is persisted queries configuration?
Persisted queries through automatic persisting, cache configuration. Set up query registry, automatic extraction. Features: query optimization, network efficiency.
How do you configure development tools?
Development tools through Apollo DevTools integration, debugging options. Set up logging, inspection tools. Features: cache inspection, query debugging.
What are type policies configuration?
Type policies through cache configuration, field definitions. Set up custom field behavior, merge functions. Features: cache normalization, field computing.
How do you set up testing environment?
Testing setup through MockedProvider, test utilities. Configure mock responses, network behavior. Features: query testing, mutation verification.
What is fragment matching configuration?
Fragment matching through IntrospectionFragmentMatcher, type configuration. Set up union types, interface handling. Features: type resolution, fragment support.
How do you configure batch operations?
Batch operations through Apollo Link Batch, queue configuration. Set up request batching, timing options. Features: request optimization, network efficiency.
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