The promise of TanStack Query is enticing: "Delete your global state management and let the cache handle it." For many teams, this works—until it doesn't. While building a highly interactive, multi-user Kanban platform, we took this advice to the extreme. We bypassed traditional state management entirely, treating our backend as the "Single Source of Truth" for every UI interaction.It worked beautifully in development. But as we scaled to hundreds of concurrent users, our "simple" architecture turned into a self-inflicted DDoS attack on our own database.In this talk, we’ll go under the hood of TanStack Query to explore why the "Invalidate and Refetch" pattern fails in high-interaction environments. We will break down the architectural shift from reactive refetching to Optimistic UI, discuss the nuances of managing granular query keys, and define the clear boundary where Server State ends and Client State must begin. You’ll leave with a blueprint for building collaborative, high-performance UIs that are kind to your infrastructure.
