When working with TanStack Query in React, ensuring efficient and scalable data fetching is crucial for delivering a smooth user experience. One key area to focus on is reducing the number of network requests your application makes, which can be achieved through batching, deduplication, and minimizing unnecessary refetches.

Batching refers to the practice of grouping multiple requests together so that they can be sent in a single network call, reducing overhead and improving performance. While TanStack Query does not batch requests by default, you can implement batching logic at the API layer or use endpoints that support batch operations.

Deduplication is handled automatically by TanStack Query. When multiple components request the same data simultaneously, TanStack Query ensures that only one network request is sent, and all components receive the same response. This prevents redundant requests and conserves bandwidth.

Minimizing unnecessary refetches is another important strategy. By carefully configuring your queries, you can avoid situations where data is refetched too frequently. This not only reduces server load but also speeds up your application for users.

A common way to tune data freshness and cache behavior is by adjusting the staleTime and gcTime options in your queries. The staleTime determines how long fetched data is considered fresh. If data is fresh, TanStack Query serves it from the cache and does not refetch it automatically. The gcTime controls how long unused data stays in the cache before it is garbage collected. By increasing staleTime, you can reduce the frequency of background refetches, and by tuning gcTime, you ensure that data is not prematurely removed from the cache.

useQuery(['user', userId], fetchUserProfile, {
  staleTime: 1000 * 60 * 10, // 10 minutes
  gcTime: 1000 * 60 * 30, // 30 minutes
});

In this configuration, the data remains fresh for 10 minutes (staleTime). During that period, TanStack Query will not refetch the data in the background, even if the component remounts or the window refocuses. The cached data will be kept in memory for 30 minutes (gcTime) after the last observer unsubscribes, reducing the chance of unnecessary network requests if the user navigates back to the profile page within that time.

To help you use TanStack Query efficiently in production, here is a checklist of best practices:

• Set appropriate staleTime and gcTime values based on how frequently your data changes;
• Avoid manual refetching unless necessary; rely on query invalidation to keep data fresh;
• Use query keys thoughtfully to maximize cache reuse and deduplication;
• Leverage automatic deduplication by structuring queries to share keys where possible;
• Monitor and profile your application to identify redundant requests or performance bottlenecks;
• Use TanStack Query Devtools to debug cache state and query behavior;
• Prefer background refetching for non-critical updates to avoid blocking the UI;
• Clean up unused queries by tuning gcTime to match your app's navigation patterns;
• Document and review your query configurations as your app scales.