TanStack Query

Why TanStack Query?

TanStack Query (formerly React Query) has fundamentally changed how React developers handle asynchronous data. It separates server state (persisted remotely, asynchronous) from client state (UI themes, form inputs), solving the complexity of caching, deduping, and background updates that traditionally required complex useEffect boilerplate or global state managers like Redux.

• Automatic Caching & Invalidation: Intelligent caching strategies that keep data fresh without manual intervention, using stale-while-revalidate patterns.
• Declarative API: Hooks like useQuery and useMutation drastically reduce code volume compared to imperative fetching logic.
• Background Synchronization: Automatically refetches data when the window focuses or the network reconnects.
• Request Deduping: Prevents multiple components from triggering identical network requests simultaneously.
• Integrated DevTools: Offers a dedicated GUI to visualize cache states, inspect query keys, and debug data flows.

Code Snippet

In v5, TanStack Query standardized on a single object argument for better type safety and extensibility.

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

// Fetcher function
const fetchTodos = async () => {
  const res = await fetch('/api/todos')
  return res.json()
}

function TodoList() {
  const queryClient = useQueryClient()

  // Query: Fetching data
  const { isPending, error, data } = useQuery({
    queryKey: ['todos'],
    queryFn: fetchTodos,
    staleTime: 1000 * 60, // Data is fresh for 1 minute
  })

  // Mutation: Updating data
  const mutation = useMutation({
    mutationFn: (newTodo) => {
      return fetch('/api/todos', {
        method: 'POST',
        body: JSON.stringify(newTodo),
      })
    },
    onSuccess: () => {
      // Invalidate and refetch
      queryClient.invalidateQueries({ queryKey: ['todos'] })
    },
  })

  if (isPending) return 'Loading...'
  if (error) return 'An error has occurred: ' + error.message

  return (
    <div>
      <ul>
        {data.map((todo) => (
          <li key={todo.id}>{todo.title}</li>
        ))}
      </ul>
      <button
        onClick={() => {
          mutation.mutate({ id: Date.now(), title: 'New Todo' })
        }}
      >
        Add Todo
      </button>
    </div>
  )
}

The code above demonstrates a standard read/write pattern. The staleTime configuration prevents unnecessary network requests, while invalidateQueries ensures the UI reflects the server state immediately after a mutation.

Pros and Cons

No library is perfect; understanding the trade-offs is key to selecting the right tool.

Pros

• Eliminates Boilerplate: Removes the need for loading, error, and data state tracking variables in useEffect.
• Backend Agnostic: Works with any function that returns a Promise (REST, GraphQL, tRPC, WebSockets).
• Robust Feature Set: Includes pagination, infinite scrolling, optimistic updates, and dependent queries out of the box.
• Excellent DX: Strong TypeScript inference and the dedicated DevTools make debugging asynchronous flows significantly easier.

Cons

• Bundle Size: Heavier than alternatives like SWR, which might be a consideration for extremely performance-sensitive micro-applications.
• Learning Curve: Understanding queryKey arrays, cache invalidation strategies, and the difference between staleTime and gcTime requires study.
• Abstraction: For very simple apps fetching a single endpoint, it introduces more complexity than a native fetch call.

Comparison with Other Data Fetching Libraries

The table below outlines the positioning differences between TanStack Query and other popular libraries to help you make an informed decision: