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

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
      refetchOnWindowFocus: false,
    },
  },
})

function App() {
  return (
    <QueryClientProvider client={queryClient}>
      <YourApp />
      <ReactQueryDevtools initialIsOpen={false} />
    </QueryClientProvider>
  )
}

npm install -D @tanstack/react-devtools

import { QueryClient, QueryClientProvider } from '@tanstack/react-query'
import { ReactQueryDevtoolsPanel } from '@tanstack/react-query-devtools'
import { TanStackDevtools } from '@tanstack/react-devtools'

function App() {
  return (
    <QueryClientProvider client={queryClient}>
      <YourApp />
      <TanStackDevtools
        config={{ position: 'bottom-right' }}
        plugins={[
          { name: 'TanStack Query', render: <ReactQueryDevtoolsPanel /> },
          // Add more plugins: Router, etc.
        ]}
      />
    </QueryClientProvider>
  )
}

import { useQuery, useMutation, useQueryClient, queryOptions } from '@tanstack/react-query'

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()
  },
})

function useTodos() {
  return useQuery(todosQueryOptions)
}

function useAddTodo() {
  const queryClient = useQueryClient()
  return useMutation({
    mutationFn: async (newTodo: { title: string }) => {
      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'] })
    },
  })
}

// Dependent queries (B waits for A)
const { data: user } = useQuery({ queryKey: ['user', id], queryFn: () => fetchUser(id) })
const { data: posts } = useQuery({
  queryKey: ['posts', user?.id],
  queryFn: () => fetchPosts(user!.id),
  enabled: !!user,
})

// Parallel queries
const results = useQueries({
  queries: ids.map(id => ({ queryKey: ['item', id], queryFn: () => fetchItem(id) })),
  combine: (results) => ({ data: results.map(r => r.data), pending: results.some(r => r.isPending) }),
})

// Prefetch on hover
const handleHover = () => queryClient.prefetchQuery({ queryKey: ['item', id], queryFn: () => fetchItem(id) })

// Infinite scroll
useInfiniteQuery({
  queryKey: ['posts'],
  queryFn: ({ pageParam }) => fetchPosts(pageParam),
  initialPageParam: 0,
  getNextPageParam: (lastPage) => lastPage.nextCursor,
})

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

// Data transformation
useQuery({ queryKey: ['todos'], queryFn: fetchTodos, select: (data) => data.filter(t => t.completed) })