What problem does it solve? Managing server state in React applications requires handling caching, background refetching, loading states, and synchronization manually, which leads to duplicated boilerplate and stale data bugs. ## Core Features & Use Cases - Query Management: Create typed queries with structured query keys, filters, dependent queries, and parallel fetching via useQueries. - Mutations with Optimistic Updates: Handle create, update, and delete operations with cache invalidation, rollback on error, and instant UI feedback. - Infinite Queries & SSR: Implement cursor or offset-based pagination with intersection observers, plus server-side prefetching and hydration for Next.js App Router. - Use Case: A developer building a Next.js dashboard needs to fetch paginated product lists, update records with instant UI feedback, and keep caches synchronized across components without writing custom state logic. ## Quick Start Set up TanStack Query in my Next.js app with a QueryClient provider, a users query hook, and a mutation with optimistic updates.