A calm, practical guide to loading, caching, and streaming data in modern React applications.

Data fetching is one of the biggest changes in the Next.js App Router era.
Instead of manually orchestrating waterfalls, suspense boundaries, and client-side fetches, Next.js encourages a server-first, cached-by-default model that results in faster and more predictable applications.

But the shift introduces new concepts:

• Where does fetch() actually run?
• When does Next.js cache responses?
• What is “revalidation”?
• How do you fetch data per segment?
• What’s the right pattern for production apps?

This chapter provides a complete, practical understanding — calm, clear, and grounded.