name: tanstack-query-best-practices
description: TanStack Query (React Query) best practices for data fetching, caching, mutations, and server state management. Activate when building data-driven React applications with server state.

TanStack Query Best Practices

Comprehensive guidelines for implementing TanStack Query (React Query) patterns in React applications. These rules optimize data fetching, caching, mutations, and server state synchronization.

When to Apply

• Creating new data fetching logic
• Setting up query configurations
• Implementing mutations and optimistic updates
• Configuring caching strategies
• Integrating with SSR/SSG
• Refactoring existing data fetching code

Rule Categories by Priority

Quick Reference

Query Keys (Prefix: qk-)

• qk-array-structure — Always use arrays for query keys
• qk-include-dependencies — Include all variables the query depends on
• qk-hierarchical-organization — Organize keys hierarchically (entity → id → filters)
• qk-factory-pattern — Use query key factories for complex applications
• qk-serializable — Ensure all key parts are JSON-serializable

Caching (Prefix: cache-)

• cache-stale-time — Set appropriate staleTime based on data volatility
• cache-gc-time — Configure gcTime for inactive query retention
• cache-defaults — Set sensible defaults at QueryClient level
• cache-invalidation — Use targeted invalidation over broad patterns
• cache-placeholder-vs-initial — Understand placeholder vs initial data differences

Mutations (Prefix: mut-)

• mut-invalidate-queries — Always invalidate related queries after mutations
• mut-optimistic-updates — Implement optimistic updates for responsive UI
• mut-rollback-context — Provide rollback context from onMutate
• mut-error-handling — Handle mutation errors gracefully
• mut-loading-states — Use isPending for mutation loading states
• mut-mutation-state — Use useMutationState for cross-component tracking

Error Handling (Prefix: err-)

• err-error-boundaries — Use error boundaries with useQueryErrorResetBoundary
• err-retry-config — Configure retry logic appropriately
• err-fallback-data — Provide fallback data when appropriate

Prefetching (Prefix: pf-)

• pf-intent-prefetch — Prefetch on user intent (hover, focus)
• pf-route-prefetch — Prefetch data during route transitions
• pf-stale-time-config — Set staleTime when prefetching
• pf-ensure-query-data — Use ensureQueryData for conditional prefetching

Infinite Queries (Prefix: inf-)

• inf-page-params — Always provide getNextPageParam
• inf-loading-guards — Check isFetchingNextPage before fetching more
• inf-max-pages — Consider maxPages for large datasets

SSR Integration (Prefix: ssr-)

• ssr-dehydration — Use dehydrate/hydrate pattern for SSR
• ssr-client-per-request — Create QueryClient per request
• ssr-stale-time-server — Set higher staleTime on server
• ssr-hydration-boundary — Wrap with HydrationBoundary

Parallel Queries (Prefix: parallel-)

• parallel-use-queries — Use useQueries for dynamic parallel queries
• query-cancellation — Implement query cancellation properly

Performance (Prefix: perf-)

• perf-select-transform — Use select to transform/filter data
• perf-structural-sharing — Leverage structural sharing
• perf-notify-change-props — Limit re-renders with notifyOnChangeProps
• perf-placeholder-data — Use placeholderData for instant UI

Offline Support (Prefix: offline-)

• network-mode — Configure network mode for offline support
• persist-queries — Configure query persistence for offline support

How to Use

Each rule file in the rules/ directory contains:
1. Explanation — Why this pattern matters
2. Bad Example — Anti-pattern to avoid
3. Good Example — Recommended implementation
4. Context — When to apply or skip this rule

Full Reference

See individual rule files in rules/ directory for detailed guidance and code examples.