How would you manually clear cached data after a user performs an action, such as creating a new post?

You call the revalidatePath or revalidateTag function inside a server action or route handler after the update completes, telling Next.js to throw away the old cached version of a specific page or tagged data so the next request fetches fresh information immediately.

'use server';
import { revalidatePath } from 'next/cache';

export async function createPost(formData) {
  await savePost(formData);
  revalidatePath('/blog');
}