Revalidation

🔍 What Is It?

Revalidation is the mechanism for invalidating and refreshing cached content in Next.js. Three strategies:

1. Time-based — next: { revalidate: 3600 } — refresh after N seconds (ISR)
2. On-demand path — revalidatePath('/products/slug') — invalidate a specific URL
3. On-demand tag — revalidateTag('products') — invalidate all content with a tag

Revalidation uses stale-while-revalidate: serve the cached version immediately, rebuild in the background, serve fresh version to subsequent requests.

🎯 Why Do We Need It?

Without revalidation, you face a binary choice:

• →SSG — fast but stale until next full deploy
• →SSR — always fresh but slow and expensive

Revalidation gives you a third option: static performance + controlled freshness. You decide exactly when content updates, either by time or by event (CMS publish, price change, stock update).

🏗️ What Happens in Real Projects?

Revalidation strategy by content type:

⚙️ How It Works

On-demand revalidation flow:

1. Editor publishes a blog post in CMS
2. CMS sends POST to /api/revalidate with { type: 'post', slug: 'my-post' }
3. Route Handler verifies webhook secret
4. Calls revalidateTag('posts') and revalidatePath('/blog/my-post')
5. Next.js marks those cache entries as stale
6. Next request to /blog/my-post triggers a background rebuild
7. Fresh HTML served to subsequent requests

💻 Example

Complete Revalidation Setup — A production-ready revalidation webhook with tag-based invalidation.

// lib/data/posts.ts
export async function getPost(slug: string) {
  const res = await fetch(
    `https://cms.example.com/posts/${slug}`,
    {
      next: {
        revalidate: 86400, // 24hr safety net
        tags: [
          'posts',           // All posts
          `post-${slug}`,  // This specific post
        ],
      },
    }
  );
  return res.json();
}

export async function getNavigation() {
  const res = await fetch('https://cms.example.com/navigation', {
    next: { revalidate: 3600, tags: ['navigation'] },
  });
  return res.json();
}

🤔 Common Confusions

🚨 Common Production Issues

✅ Best Practices

🏛️ Architect's Note

💬 Frequently Asked Questions

🎯 Key Takeaways

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