6. Revalidate - Time-Based and On-Demand

With the { next: { revalidate: 3600 } } pattern covered previously, data only refreshes after the exact predefined interval elapses, even if a triggering event (such as an admin publishing a new post) occurs much earlier. On-demand revalidation eliminates this unnecessary lag.

1. The limitation of time-based revalidation

• Example: an article feed page uses revalidate: 3600 (1 hour). An admin publishes a new article, yet that post will take up to an hour to show up, even though the exact moment requiring cache invalidation (immediately post-publish) is precisely known.

2. revalidatePath: instantly revalidating a specific URL path

'use server';
import { revalidatePath } from 'next/cache';
 
async function createPost(data) {
  await db.post.create({ data });
  revalidatePath('/blog'); // the next request to /blog receives fresh data immediately
}

• Used when you know the exact single path that needs invalidation.

3. revalidateTag: bulk revalidating multiple targets with a single call

• The issue: if a new post appears across several distinct pages (/blog, /, /authors/[id]), using revalidatePath requires invoking it individually for each route, making it easy to miss locations.
• Solution: attach tags to fetch() calls across all related contexts, even if the underlying API endpoints differ:

const posts = await fetch('[https://api.example.com/posts](https://api.example.com/posts)', {
  next: { tags: ['posts'] }
});

• A single function call prompts Next.js to locate and purge every cached payload tagged with that key, without needing an exhaustive list of individual paths:

revalidateTag('posts');

4. When to choose which

• revalidatePath: you know the exact, isolated URL path that requires purging.
• revalidateTag: the same data entity is shared across multiple disjointed views, making an exhaustive list of paths impractical or fragile.
• Both are typically executed within Server Actions or Route Handlers, immediately following successful write operations (create/update/delete).