Interview Questions
Query variables through useQuery options, variable definitions. Support default values, type safety. Features: variable validation, dynamic updates. Consider variable scoping, reusability.
Polling through pollInterval option in useQuery. Configure interval timing, automatic updates. Features: start/stop polling, skip conditions. Consider server load, real-time requirements.
Refetching through refetch function, network-only policy. Support manual/automatic triggers, variables update. Features: selective refetching, loading states. Consider cache invalidation, performance.
Optimization through field selection, pagination. Implement proper caching, batching. Features: minimal queries, efficient loading. Consider data requirements, network usage.
Directives modify query execution behavior. Implement @skip, @include, custom directives. Features: conditional fields, runtime control. Consider schema support, client capabilities.
Testing through mock providers, test utilities. Implement unit tests, integration tests. Features: query mocking, response simulation. Consider test coverage, maintenance.
Error handling through errorPolicy option, error results. Implement error boundaries, retry logic. Features: partial data handling, error recovery. Consider user experience, error reporting.
Query signatures uniquely identify operations. Used for caching, deduplication. Features: automatic generation, query identification. Consider cache keys, operation tracking.
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.
Skip/Include directives for conditional field inclusion. Control field selection at runtime. Features: dynamic queries, conditional data. Consider query complexity, performance impact.
Cancellation through AbortController, cleanup functions. Handle component unmount, user actions. Features: request termination, resource cleanup. Consider in-flight requests, state management.
Context provides global query configuration. Share data between resolvers, links. Features: auth tokens, headers management. Consider request lifecycle, security implications.
Dynamic queries using query variables, conditional fields. Implement skip/include directives. Features: runtime variables, dynamic field selection. Consider query complexity, caching implications.
Loading states: loading, error, data, networkStatus. Access through useQuery hook result. Features: partial data handling, refetch status. Important for user feedback, error handling.
Prefetching through client.query, preloadQuery. Improve perceived performance, data availability. Features: cache warming, anticipatory loading. Consider resource usage, timing.
Standby policy pauses query execution. Useful for inactive queries, resource management. Features: manual execution control, cache preservation. Consider memory usage, query prioritization.
Deduplication combines identical concurrent requests. Reduces network traffic, improves performance. Features: automatic caching, request optimization. Consider cache policies, timing.
Persistence through cache storage, local state. Implement offline support, data retention. Features: cache serialization, state recovery. Consider storage limits, data privacy.
Timeouts through Apollo Link configuration. Implement timeout logic, error handling. Features: custom timeout values, cancel operations. Consider network conditions, user experience.
NotifyOnNetworkStatusChange tracks detailed network status. Provides component updates for network changes. Features: refetch status, error states. Important for loading indicators, error handling.
Authorization through context, directives. Implement access control, role checks. Features: permission handling, secure queries. Consider security requirements, user roles.
Organization through query separation, fragments. Implement colocated queries, reusable parts. Features: maintainable structure, type safety. Consider code reuse, maintainability.
Partial responses through errorPolicy: 'all'. Handle missing fields, null values. Features: partial data rendering, error boundaries. Consider user experience, data completeness.
Query batching combines multiple queries into single request. Implement through Apollo Link batch. Features: automatic batching, timeout configuration. Consider network optimization, request timing.
Monitoring through Apollo Studio, custom metrics. Track performance, errors, usage patterns. Features: analytics, debugging tools. Consider monitoring strategy, performance impact.
TypeScript support through codegen, type definitions. Implement type safety, variable validation. Features: automatic types, compile-time checks. Consider development experience, maintenance.
Nested queries through proper field selection, fragments. Implement efficient data loading, caching. Features: normalized data, relationship handling. Consider query complexity, performance.
Error recovery through retry logic, fallback data. Implement error boundaries, user feedback. Features: graceful degradation, recovery options. Consider user experience, data integrity.
Retry logic through retry link configuration. Handle network errors, timeout scenarios. Features: exponential backoff, max attempts. Consider error types, retry conditions.
Cost analysis evaluates query complexity, resource usage. Implement limits, optimization suggestions. Features: query validation, performance metrics. Consider server resources, scalability.