Konghayao Zen Code 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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