Yoriichi Dang Dashboard Web Template Tanstack Query

TanStack Query (React Query) v5

Last Updated: 2026-01-20 Versions: @tanstack/react-query@5.90.19, @tanstack/react-query-devtools@5.91.2 Requires: React 18.0+ (useSyncExternalStore), TypeScript 4.7+ (recommended)

v5 New Features

useMutationState - Cross-Component Mutation Tracking

Access mutation state from anywhere without prop drilling:

import { useMutationState } from '@tanstack/react-query'

function GlobalLoadingIndicator() {
  // Get all pending mutations
  const pendingMutations = useMutationState({
    filters: { status: 'pending' },
    select: (mutation) => mutation.state.variables,
  })

  if (pendingMutations.length === 0) return null
  return <div>Saving {pendingMutations.length} items...</div>
}

// Filter by mutation key
const todoMutations = useMutationState({
  filters: { mutationKey: ['addTodo'] },
})

Simplified Optimistic Updates

New pattern using variables - no cache manipulation, no rollback needed:

function TodoList() {
  const { data: todos } = useQuery({ queryKey: ['todos'], queryFn: fetchTodos })

  const addTodo = useMutation({
    mutationKey: ['addTodo'],
    mutationFn: (newTodo) => api.addTodo(newTodo),
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: ['todos'] })
    },
  })

  // Show optimistic UI using variables from pending mutations
  const pendingTodos = useMutationState({
    filters: { mutationKey: ['addTodo'], status: 'pending' },
    select: (mutation) => mutation.state.variables,
  })

  return (
    <ul>
      {todos?.map(todo => <li key={todo.id}>{todo.title}</li>)}
      {/* Show pending items with visual indicator */}
      {pendingTodos.map((todo, i) => (
        <li key={`pending-${i}`} style={{ opacity: 0.5 }}>{todo.title}</li>
      ))}
    </ul>
  )
}

throwOnError - Error Boundaries

Renamed from useErrorBoundary (breaking change):

import { QueryErrorResetBoundary } from '@tanstack/react-query'
import { ErrorBoundary } from 'react-error-boundary'

function App() {
  return (
    <QueryErrorResetBoundary>
      {({ reset }) => (
        <ErrorBoundary fallbackRender={({ resetErrorBoundary }) => (
          <div>
            Error! <button
          </div>
        )}>
          <Todos />
        </ErrorBoundary>
      )}
    </QueryErrorResetBoundary>
  )
}

function Todos() {
  const { data } = useQuery({
    queryKey: ['todos'],
    queryFn: fetchTodos,
    throwOnError: true, // ✅ v5 (was useErrorBoundary in v4)
  })
  return <div>{data.map(...)}</div>
}

Network Mode (Offline/PWA Support)

Control behavior when offline:

const queryClient = new QueryClient({
  defaultOptions: {
    queries: {
      networkMode: 'offlineFirst', // Use cache when offline
    },
  },
})

// Per-query override
useQuery({
  queryKey: ['todos'],
  queryFn: fetchTodos,
  networkMode: 'always', // Always try, even offline (for local APIs)
})

Detecting paused state:

const { isPending, fetchStatus } = useQuery(...)
// isPending + fetchStatus === 'paused' = offline, waiting for network

useQueries with Combine

Combine results from parallel queries:

const results = useQueries({
  queries: userIds.map(id => ({
    queryKey: ['user', id],
    queryFn: () => fetchUser(id),
  })),
  combine: (results) => ({
    data: results.map(r => r.data),
    pending: results.some(r => r.isPending),
    error: results.find(r => r.error)?.error,
  }),
})

// Access combined result
if (results.pending) return <Loading />
console.log(results.data) // [user1, user2, user3]

infiniteQueryOptions Helper

Type-safe factory for infinite queries (parallel to queryOptions):

import { infiniteQueryOptions, useInfiniteQuery, prefetchInfiniteQuery } from '@tanstack/react-query'

const todosInfiniteOptions = infiniteQueryOptions({
  queryKey: ['todos', 'infinite'],
  queryFn: ({ pageParam }) => fetchTodosPage(pageParam),
  initialPageParam: 0,
  getNextPageParam: (lastPage) => lastPage.nextCursor,
})

// Reuse across hooks
useInfiniteQuery(todosInfiniteOptions)
useSuspenseInfiniteQuery(todosInfiniteOptions)
prefetchInfiniteQuery(queryClient, todosInfiniteOptions)

maxPages - Memory Optimization

Limit pages stored in cache for infinite queries:

useInfiniteQuery({
  queryKey: ['posts'],
  queryFn: ({ pageParam }) => fetchPosts(pageParam),
  initialPageParam: 0,
  getNextPageParam: (lastPage) => lastPage.nextCursor,
  getPreviousPageParam: (firstPage) => firstPage.prevCursor, // Required with maxPages
  maxPages: 3, // Only keep 3 pages in memory
})

Note: maxPages requires bi-directional pagination (getNextPageParam AND getPreviousPageParam).

Quick Setup

npm install @tanstack/react-query@latest
npm install -D @tanstack/react-query-devtools@latest

Step 2: Provider + Config

// src/main.tsx
import { QueryClient, QueryClientProvider } from '@tanstack/react-query'
import { ReactQueryDevtools } from '@tanstack/react-query-devtools'

const queryClient = new QueryClient({
  defaultOptions: {
    queries: {
      staleTime: 1000 * 60 * 5, // 5 min
      gcTime: 1000 * 60 * 60, // 1 hour (v5: renamed from cacheTime)
      refetchOnWindowFocus: false,
    },
  },
})

<QueryClientProvider client={queryClient}>
  <App />
  <ReactQueryDevtools initialIsOpen={false} />
</QueryClientProvider>

Step 3: Query + Mutation Hooks

// src/hooks/useTodos.ts
import { useQuery, useMutation, useQueryClient, queryOptions } from '@tanstack/react-query'

// Query options factory (v5 pattern)
export const todosQueryOptions = queryOptions({
  queryKey: ['todos'],
  queryFn: async () => {
    const res = await fetch('/api/todos')
    if (!res.ok) throw new Error('Failed to fetch')
    return res.json()
  },
})

export function useTodos() {
  return useQuery(todosQueryOptions)
}

export function useAddTodo() {
  const queryClient = useQueryClient()
  return useMutation({
    mutationFn: async (newTodo) => {
      const res = await fetch('/api/todos', {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify(newTodo),
      })
      if (!res.ok) throw new Error('Failed to add')
      return res.json()
    },
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: ['todos'] })
    },
  })
}

// Usage:
function TodoList() {
  const { data, isPending, isError, error } = useTodos()
  const { mutate } = useAddTodo()

  if (isPending) return <div>Loading...</div>
  if (isError) return <div>Error: {error.message}</div>
  return <ul>{data.map(todo => <li key={todo.id}>{todo.title}</li>)}</ul>
}

Critical Rules

Always Do

✅ Use object syntax for all hooks

// v5 ONLY supports this:
useQuery({ queryKey, queryFn, ...options })
useMutation({ mutationFn, ...options })

✅ Use array query keys

queryKey: ['todos']              // List
queryKey: ['todos', id]          // Detail
queryKey: ['todos', { filter }]  // Filtered

✅ Configure staleTime appropriately

staleTime: 1000 * 60 * 5 // 5 min - prevents excessive refetches

✅ Use isPending for initial loading state

if (isPending) return <Loading />
// isPending = no data yet AND fetching

✅ Throw errors in queryFn

if (!response.ok) throw new Error('Failed')

✅ Invalidate queries after mutations

onSuccess: () => {
  queryClient.invalidateQueries({ queryKey: ['todos'] })
}

✅ Use queryOptions factory for reusable patterns

const opts = queryOptions({ queryKey, queryFn })
useQuery(opts)
useSuspenseQuery(opts)
prefetchQuery(opts)

✅ Use gcTime (not cacheTime)

gcTime: 1000 * 60 * 60 // 1 hour

Never Do

❌ Never use v4 array/function syntax

// v4 (removed in v5):
useQuery(['todos'], fetchTodos, options) // ❌

// v5 (correct):
useQuery({ queryKey: ['todos'], queryFn: fetchTodos }) // ✅

❌ Never use query callbacks (onSuccess, onError, onSettled in queries)

// v5 removed these from queries:
useQuery({
  queryKey: ['todos'],
  queryFn: fetchTodos,
  onSuccess: (data) => {}, // ❌ Removed in v5
})

// Use useEffect instead:
const { data } = useQuery({ queryKey: ['todos'], queryFn: fetchTodos })
useEffect(() => {
  if (data) {
    // Do something
  }
}, [data])

// Or use mutation callbacks (still supported):
useMutation({
  mutationFn: addTodo,
  onSuccess: () => {}, // ✅ Still works for mutations
})

❌ Never use deprecated options

// Deprecated in v5:
cacheTime: 1000 // ❌ Use gcTime instead
isLoading: true // ❌ Meaning changed, use isPending
keepPreviousData: true // ❌ Use placeholderData instead
onSuccess: () => {} // ❌ Removed from queries
useErrorBoundary: true // ❌ Use throwOnError instead

❌ Never assume isLoading means "no data yet"

// v5 changed this:
isLoading = isPending && isFetching // ❌ Now means "pending AND fetching"
isPending = no data yet // ✅ Use this for initial load

❌ Never forget initialPageParam for infinite queries

// v5 requires this:
useInfiniteQuery({
  queryKey: ['projects'],
  queryFn: ({ pageParam }) => fetchProjects(pageParam),
  initialPageParam: 0, // ✅ Required in v5
  getNextPageParam: (lastPage) => lastPage.nextCursor,
})

❌ Never use enabled with useSuspenseQuery

// Not allowed:
useSuspenseQuery({
  queryKey: ['todo', id],
  queryFn: () => fetchTodo(id),
  enabled: !!id, // ❌ Not available with suspense
})

// Use conditional rendering instead:
{id && <TodoComponent id={id} />}

❌ Never rely on refetchOnMount: false for errored queries

// Doesn't work - errors are always stale
useQuery({
  queryKey: ['data'],
  queryFn: failingFetch,
  refetchOnMount: false,  // ❌ Ignored when query has error
})

// Use retryOnMount instead
useQuery({
  queryKey: ['data'],
  queryFn: failingFetch,
  refetchOnMount: false,
  retryOnMount: false,  // ✅ Prevents refetch for errored queries
  retry: 0,
})

Known Issues Prevention

This skill prevents 16 documented issues from v5 migration, SSR/hydration bugs, and common mistakes:

Issue #1: Object Syntax Required

Error: useQuery is not a function or type errors Source: v5 Migration Guide Why It Happens: v5 removed all function overloads, only object syntax works Prevention: Always use useQuery({ queryKey, queryFn, ...options })

Before (v4):

useQuery(['todos'], fetchTodos, { staleTime: 5000 })

After (v5):

useQuery({
  queryKey: ['todos'],
  queryFn: fetchTodos,
  staleTime: 5000
})

Issue #2: Query Callbacks Removed

Error: Callbacks don't run, TypeScript errors Source: v5 Breaking Changes Why It Happens: onSuccess, onError, onSettled removed from queries (still work in mutations) Prevention: Use useEffect for side effects, or move logic to mutation callbacks

Before (v4):

useQuery({
  queryKey: ['todos'],
  queryFn: fetchTodos,
  onSuccess: (data) => {
    console.log('Todos loaded:', data)
  },
})

After (v5):

const { data } = useQuery({ queryKey: ['todos'], queryFn: fetchTodos })
useEffect(() => {
  if (data) {
    console.log('Todos loaded:', data)
  }
}, [data])

Issue #3: Status Loading → Pending

Error: UI shows wrong loading state Source: v5 Migration: isLoading renamed Why It Happens: status: 'loading' renamed to status: 'pending', isLoading meaning changed Prevention: Use isPending for initial load, isLoading for "pending AND fetching"

Before (v4):

const { data, isLoading } = useQuery(...)
if (isLoading) return <div>Loading...</div>

After (v5):

const { data, isPending, isLoading } = useQuery(...)
if (isPending) return <div>Loading...</div>
// isLoading = isPending && isFetching (fetching for first time)

Issue #4: cacheTime → gcTime

Error: cacheTime is not a valid option Source: v5 Migration: gcTime Why It Happens: Renamed to better reflect "garbage collection time" Prevention: Use gcTime instead of cacheTime

Before (v4):

useQuery({
  queryKey: ['todos'],
  queryFn: fetchTodos,
  cacheTime: 1000 * 60 * 60,
})

After (v5):

useQuery({
  queryKey: ['todos'],
  queryFn: fetchTodos,
  gcTime: 1000 * 60 * 60,
})

Issue #5: useSuspenseQuery + enabled

Error: Type error, enabled option not available Source: GitHub Discussion #6206 Why It Happens: Suspense guarantees data is available, can't conditionally disable Prevention: Use conditional rendering instead of enabled option

Before (v4/incorrect):

useSuspenseQuery({
  queryKey: ['todo', id],
  queryFn: () => fetchTodo(id),
  enabled: !!id, // ❌ Not allowed
})

After (v5/correct):

// Conditional rendering:
{id ? (
  <TodoComponent id={id} />
) : (
  <div>No ID selected</div>
)}

// Inside TodoComponent:
function TodoComponent({ id }: { id: number }) {
  const { data } = useSuspenseQuery({
    queryKey: ['todo', id],
    queryFn: () => fetchTodo(id),
    // No enabled option needed
  })
  return <div>{data.title}</div>
}

Issue #6: initialPageParam Required

Error: initialPageParam is required type error Source: v5 Migration: Infinite Queries Why It Happens: v4 passed undefined as first pageParam, v5 requires explicit value Prevention: Always specify initialPageParam for infinite queries

Before (v4):

useInfiniteQuery({
  queryKey: ['projects'],
  queryFn: ({ pageParam = 0 }) => fetchProjects(pageParam),
  getNextPageParam: (lastPage) => lastPage.nextCursor,
})

After (v5):

useInfiniteQuery({
  queryKey: ['projects'],
  queryFn: ({ pageParam }) => fetchProjects(pageParam),
  initialPageParam: 0, // ✅ Required
  getNextPageParam: (lastPage) => lastPage.nextCursor,
})

Issue #7: keepPreviousData Removed

Error: keepPreviousData is not a valid option Source: v5 Migration: placeholderData Why It Happens: Replaced with more flexible placeholderData function Prevention: Use placeholderData: keepPreviousData helper

Before (v4):

useQuery({
  queryKey: ['todos', page],
  queryFn: () => fetchTodos(page),
  keepPreviousData: true,
})

After (v5):

import { keepPreviousData } from '@tanstack/react-query'

useQuery({
  queryKey: ['todos', page],
  queryFn: () => fetchTodos(page),
  placeholderData: keepPreviousData,
})

Issue #8: TypeScript Error Type Default

Error: Type errors with error handling Source: v5 Migration: Error Types Why It Happens: v4 used unknown, v5 defaults to Error type Prevention: If throwing non-Error types, specify error type explicitly

Before (v4 - error was unknown):

const { error } = useQuery({
  queryKey: ['data'],
  queryFn: async () => {
    if (Math.random() > 0.5) throw 'custom error string'
    return data
  },
})
// error: unknown

After (v5 - specify custom error type):

const { error } = useQuery<DataType, string>({
  queryKey: ['data'],
  queryFn: async () => {
    if (Math.random() > 0.5) throw 'custom error string'
    return data
  },
})
// error: string | null

// Or better: always throw Error objects
const { error } = useQuery({
  queryKey: ['data'],
  queryFn: async () => {
    if (Math.random() > 0.5) throw new Error('custom error')
    return data
  },
})
// error: Error | null (default)

Issue #9: Streaming Server Components Hydration Error

Error: Hydration failed because the initial UI does not match what was rendered on the server Source: GitHub Issue #9642 Affects: v5.82.0+ with streaming SSR (void prefetch pattern) Why It Happens: Race condition where hydrate() resolves synchronously but query.fetch() creates async retryer, causing isFetching/isStale mismatch between server and client Prevention: Don't conditionally render based on fetchStatus with useSuspenseQuery and streaming prefetch, OR await prefetch instead of void pattern

Before (causes hydration error):

// Server: void prefetch
streamingQueryClient.prefetchQuery({ queryKey: ['data'], queryFn: getData });

// Client: conditional render on fetchStatus
const { data, isFetching } = useSuspenseQuery({ queryKey: ['data'], queryFn: getData });
return <>{data && <div>{data}</div>} {isFetching && <Loading />}</>;

After (workaround):

// Option 1: Await prefetch
await streamingQueryClient.prefetchQuery({ queryKey: ['data'], queryFn: getData });

// Option 2: Don't render based on fetchStatus with Suspense
const { data } = useSuspenseQuery({ queryKey: ['data'], queryFn: getData });
return <div>{data}</div>;  // No conditional on isFetching

Status: Known issue, being investigated by maintainers. Requires implementation of getServerSnapshot in useSyncExternalStore.

Issue #10: useQuery Hydration Error with Prefetching

Error: Text content mismatch during hydration Source: GitHub Issue #9399 Affects: v5.x with server-side prefetching Why It Happens: tryResolveSync detects resolved promises in RSC payload and extracts data synchronously during hydration, bypassing normal pending state Prevention: Use useSuspenseQuery instead of useQuery for SSR, or avoid conditional rendering based on isLoading

Before (causes hydration error):

// Server Component
const queryClient = getServerQueryClient();
await queryClient.prefetchQuery({ queryKey: ['todos'], queryFn: fetchTodos });

// Client Component
function Todos() {
  const { data, isLoading } = useQuery({ queryKey: ['todos'], queryFn: fetchTodos });
  if (isLoading) return <div>Loading...</div>;  // Server renders this
  return <div>{data.length} todos</div>;  // Client hydrates with this
}

After (workaround):

// Use useSuspenseQuery instead
function Todos() {
  const { data } = useSuspenseQuery({ queryKey: ['todos'], queryFn: fetchTodos });
  return <div>{data.length} todos</div>;
}

Status: "At the top of my OSS list of things to fix" - maintainer Ephem (Nov 2025). Requires implementing getServerSnapshot in useSyncExternalStore.

Issue #11: refetchOnMount Not Respected for Errored Queries

Error: Queries refetch on mount despite refetchOnMount: false Source: GitHub Issue #10018 Affects: v5.90.16+ Why It Happens: Errored queries with no data are always treated as stale. This is intentional to avoid permanently showing error states Prevention: Use retryOnMount: false instead of (or in addition to) refetchOnMount: false

Before (refetches despite setting):

const { data, error } = useQuery({
  queryKey: ['data'],
  queryFn: () => { throw new Error('Fails') },
  refetchOnMount: false,  // Ignored when query is in error state
  retry: 0,
});
// Query refetches every time component mounts

After (correct):

const { data, error } = useQuery({
  queryKey: ['data'],
  queryFn: failingFetch,
  refetchOnMount: false,
  retryOnMount: false,  // ✅ Prevents refetch on mount for errored queries
  retry: 0,
});

Status: Documented behavior (intentional). The name retryOnMount is slightly misleading - it controls whether errored queries trigger a new fetch on mount, not automatic retries.

Issue #12: Mutation Callback Signature Breaking Change (v5.89.0)

Error: TypeScript errors in mutation callbacks Source: GitHub Issue #9660 Affects: v5.89.0+ Why It Happens: onMutateResult parameter added between variables and context, changing callback signatures from 3 params to 4 Prevention: Update all mutation callbacks to accept 4 parameters instead of 3

Before (v5.88 and earlier):

useMutation({
  mutationFn: addTodo,
  onError: (error, variables, context) => {
    // context is now onMutateResult, missing final context param
  },
  onSuccess: (data, variables, context) => {
    // Same issue
  }
});

After (v5.89.0+):

useMutation({
  mutationFn: addTodo,
  onError: (error, variables, onMutateResult, context) => {
    // value from onMutate
    // context = mutation function context
  },
  onSuccess: (data, variables, onMutateResult, context) => {
    // Correct signature with 4 parameters
  }
});

Note: If you don't use onMutate, the onMutateResult parameter will be undefined. This breaking change was introduced in a patch version.

Issue #13: Readonly Query Keys Break Partial Matching (v5.90.8)

Error: Type 'readonly ["todos", string]' is not assignable to type '["todos", string]' Source: GitHub Issue #9871 | Fixed in PR #9872 Affects: v5.90.8 only (fixed in v5.90.9) Why It Happens: Partial query matching broke TypeScript types for readonly query keys (using as const) Prevention: Upgrade to v5.90.9+ or use type assertions if stuck on v5.90.8

Before (v5.90.8 - TypeScript error):

export function todoQueryKey(id?: string) {
  return id ? ['todos', id] as const : ['todos'] as const;
}
// Type: readonly ['todos', string] | readonly ['todos']

useMutation({
  mutationFn: addTodo,
  onSuccess: () => {
    queryClient.invalidateQueries({
      queryKey: todoQueryKey('123')
      // Error: readonly ['todos', string] not assignable to ['todos', string]
    });
  }
});

After (v5.90.9+):

// Works correctly with readonly types
queryClient.invalidateQueries({
  queryKey: todoQueryKey('123')  // ✅ No type error
});

Status: Fixed in v5.90.9. Particularly affected users of code generators like openapi-react-query that produce readonly query keys.

Issue #14: useMutationState Type Inference Lost

Error: mutation.state.variables typed as unknown instead of actual type Source: GitHub Issue #9825 Affects: All v5.x versions Why It Happens: Fuzzy mutation key matching prevents guaranteed type inference (same issue as queryClient.getQueryCache().find()) Prevention: Explicitly cast types in the select callback

Before (type inference doesn't work):

const addTodo = useMutation({
  mutationKey: ['addTodo'],
  mutationFn: (todo: Todo) => api.addTodo(todo),
});

const pendingTodos = useMutationState({
  filters: { mutationKey: ['addTodo'], status: 'pending' },
  select: (mutation) => {
    return mutation.state.variables;  // Type: unknown
  },
});

After (with explicit cast):

const pendingTodos = useMutationState({
  filters: { mutationKey: ['addTodo'], status: 'pending' },
  select: (mutation) => mutation.state.variables as Todo,
});
// Or cast the entire state:
select: (mutation) => mutation.state as MutationState<Todo, Error, Todo, unknown>

Status: Known limitation of fuzzy matching. No planned fix.

Issue #15: Query Cancellation in StrictMode with fetchQuery

Error: CancelledError when using fetchQuery() with useQuery Source: GitHub Issue #9798 Affects: Development only (React StrictMode) Why It Happens: StrictMode causes double mount/unmount. When useQuery unmounts and is the last observer, it cancels the query even if fetchQuery() is also running Prevention: This is expected development-only behavior. Doesn't affect production

Example:

async function loadData() {
  try {
    const data = await queryClient.fetchQuery({
      queryKey: ['data'],
      queryFn: fetchData,
    });
    console.log('Loaded:', data);  // Never logs in StrictMode
  } catch (error) {
    console.error('Failed:', error);  // CancelledError
  }
}

function Component() {
  const { data } = useQuery({ queryKey: ['data'], queryFn: fetchData });
  // In StrictMode, component unmounts/remounts, cancelling fetchQuery
}

Workaround:

// Keep query observed with staleTime
const { data } = useQuery({
  queryKey: ['data'],
  queryFn: fetchData,
  staleTime: Infinity,  // Keeps query active
});

Status: Expected StrictMode behavior, not a bug. Production builds are unaffected.

Issue #16: invalidateQueries Only Refetches Active Queries

Error: Inactive queries not refetching despite invalidateQueries() call Source: GitHub Issue #9531 Affects: All v5.x versions Why It Happens: Documentation was misleading - invalidateQueries() only refetches "active" queries by default, not "all" queries Prevention: Use refetchType: 'all' to force refetch of inactive queries

Default behavior:

// Only active queries (currently being observed) will refetch
queryClient.invalidateQueries({ queryKey: ['todos'] });

To refetch inactive queries:

queryClient.invalidateQueries({
  queryKey: ['todos'],
  refetchType: 'all'  // Refetch active AND inactive
});

Status: Documentation fixed to clarify "active" queries. This is the intended behavior.

Community Tips

Note: These tips come from community experts and maintainer blogs. Verify against your version.

Tip: Query Options with Multiple Listeners

Source: TkDodo's Blog - API Design Lessons | Confidence: HIGH Applies to: v5.27.3+

When multiple components use the same query with different options (like staleTime), the "last write wins" rule applies for future fetches, but the current in-flight query uses its original options. This can cause unexpected behavior when components mount at different times.

Example of unexpected behavior:

// Component A mounts first
function ComponentA() {
  const { data } = useQuery({
    queryKey: ['todos'],
    queryFn: fetchTodos,
    staleTime: 5000,  // Applied initially
  });
}

// Component B mounts while A's query is in-flight
function ComponentB() {
  const { data } = useQuery({
    queryKey: ['todos'],
    queryFn: fetchTodos,
    staleTime: 60000,  // Won't affect current fetch, only future ones
  });
}

Recommended approach:

// Write options as functions that reference latest values
const getStaleTime = () => shouldUseLongCache ? 60000 : 5000;

useQuery({
  queryKey: ['todos'],
  queryFn: fetchTodos,
  staleTime: getStaleTime(),  // Evaluated on each render
});

Tip: refetch() is NOT for Changed Parameters

Source: Avoiding Common Mistakes with TanStack Query | Confidence: HIGH

The refetch() function should ONLY be used for refreshing with the same parameters (like a manual "reload" button). For new parameters (filters, page numbers, search terms, etc.), include them in the query key instead.

Anti-pattern:

// ❌ Wrong - using refetch() for different parameters
const [page, setPage] = useState(1);
const { data, refetch } = useQuery({
  queryKey: ['todos'],  // Same key for all pages
  queryFn: () => fetchTodos(page),
});

// This refetches with OLD page value, not new one
<button => { setPage(2); refetch(); }}>Next</button>

Correct pattern:

// ✅ Correct - include parameters in query key
const [page, setPage] = useState(1);
const { data } = useQuery({
  queryKey: ['todos', page],  // Key changes with page
  queryFn: () => fetchTodos(page),
  // Query automatically refetches when page changes
});

<button => setPage(2)}>Next</button>  // Just update state

When to use refetch():

// ✅ Manual refresh of same data (refresh button)
const { data, refetch } = useQuery({
  queryKey: ['todos'],
  queryFn: fetchTodos,
});

<button => refetch()}>Refresh</button>  // Same parameters

Key Patterns

Dependent Queries (Query B waits for Query A):

const { data: posts } = useQuery({
  queryKey: ['users', userId, 'posts'],
  queryFn: () => fetchUserPosts(userId),
  enabled: !!user, // Wait for user
})

Parallel Queries (fetch multiple at once):

const results = useQueries({
  queries: ids.map(id => ({ queryKey: ['todos', id], queryFn: () => fetchTodo(id) })),
})

Prefetching (preload on hover):

queryClient.prefetchQuery({ queryKey: ['todo', id], queryFn: () => fetchTodo(id) })

Infinite Scroll (useInfiniteQuery):

useInfiniteQuery({
  queryKey: ['todos', 'infinite'],
  queryFn: ({ pageParam }) => fetchTodosPage(pageParam),
  initialPageParam: 0, // Required in v5
  getNextPageParam: (lastPage) => lastPage.nextCursor,
})

Query Cancellation (auto-cancel on queryKey change):

queryFn: async ({ signal }) => {
  const res = await fetch(`/api/todos?q=${search}`, { signal })
  return res.json()
}

Data Transformation (select):

select: (data) => data.filter(todo => todo.completed)

Avoid Request Waterfalls: Fetch in parallel when possible (don't chain queries unless truly dependent)

Official Docs: https://tanstack.com/query/latest | v5 Migration: https://tanstack.com/query/latest/docs/framework/react/guides/migrating-to-v5 | GitHub: https://github.com/TanStack/query | Context7: /websites/tanstack_query

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