Intro to TanStack DB: Reactive Data Layer for Modern Web Apps

TanStack DB is a reactive, local-first data layer that works alongside TanStack Query in React apps. While TanStack Query handles server communication (fetching, caching, revalidation), TanStack DB stores that data in a queryable in-browser database with proper relationships. A to-do app walkthrough demonstrates setting up collections, using `useLiveQuery` for automatic UI reactivity, implementing optimistic updates, and connecting to a simulated backend. The post also explains differential dataflow—the engine behind TanStack DB's performance—which only recomputes what changed rather than recalculating entire datasets, making it dramatically faster at scale. TanStack DB is best suited for apps with relational data, complex client-side queries, real-time updates, or offline-first requirements.