Secure Next.js Server Actions: zod Validation, useActionState, Error Handling and Auth Checks

A Server Action is a public POST endpoint, not a private function. Authenticate, validate with zod, authorize per resource and return safe errors to useActionState.

Next.js App Router Caching: fetch Cache, revalidate, ISR, revalidateTag and updateTag

Stale prices and leaked user data both come from misunderstood caching. Learn the Next.js layers, ISR, tags, updateTag vs revalidateTag, and when a route goes dynamic.

Next.js App Router: Server Components vs Client Components

Server Components run only on the server; Client Components hydrate in the browser. See how Next.js App Router renders both, and when to actually reach for 'use client'.