What is the best way to cache and sync deeply nested JSON state in React?

Cache deeply nested JSON in React using TanStack Query with normalized data structures and strategic query organization. Flatten deeply nested structures into separate queries by entity type rather than storing entire hierarchies in single cache entries. Use query keys that reflect data relationships: ["user", userId], ["posts", userId]. Implement data normalization separating entities and references similar to Redux normalized state. Use React Query dependent queries where child data depends on parent: enabled: !!userId. For real-time sync, combine TanStack Query with WebSocket updates triggering cache invalidation. Implement selective query invalidation invalidating only affected data branches. Use staleTime and cacheTime strategically: longer for stable nested data, shorter for frequently changing. Persist cache to localStorage with persistQueryClient for offline support. Structure selectors to derive nested views from flat cache. Validate nested JSON with our JSON Viewer at jsonconsole.com/json-viewer when designing cache strategy. Avoid storing entire nested hierarchies in single cache keys as updates become expensive. Normalize, cache separately, and compose in components for optimal performance and synchronization.