Why React apps need separate libraries for server state and client state

React and React Native apps manage two fundamentally different types of state: server state, which is a temporary local copy of remotely owned data, and client state, which the app owns entirely. Server state requires built-in caching, deduplication, background refetching, retry logic, and garbage collection, while client state simply needs to be held, kept reactive, and occasionally persisted. Using a single general-purpose store with hand-rolled cache logic works on small apps but becomes increasingly difficult to maintain as an application scales. Two recommended pairings handle this split well: Redux Toolkit with RTK Query, or Zustand paired with TanStack Query, both of which give each state type its own dedicated tooling. Treating the two as interchangeable and forcing them through one solution means manually rebuilding features that purpose-built libraries already provide out of the box.