TanStack Query Explained: Server State Management for Modern Web Apps

TanStack Query, formerly known as React Query, is a framework-agnostic library built to manage server state, including data fetching, caching, and background updates. Unlike client state, which lives entirely in the browser, server state is owned by a remote backend and the browser holds only a temporary snapshot. By default, cached data is stored in the browser tab's JavaScript RAM, though developers can optionally persist it to localStorage, sessionStorage, or IndexedDB via built-in persisters. The library provides core hooks such as useQuery for reading data and useMutation for writing data, with cache invalidation handled automatically on successful mutations. A configurable staleTime option controls how long fetched data is considered fresh before a background refetch is triggered.