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On Demand Revalidation

Why do we need it?​

Caching is a great way to improve the performance of your app. But, sometimes you need to revalidate the cache when the data changes. This is where on-demand revalidation comes in handy.

On-demand revalidation is a feature that allows you to revalidate the cache whenever you want. So, you won't have to wait for the cache to expire to get the latest data.

How to use it?​

In order to use on-demand revalidation, we need to add some configuration in the server.ts file.

export function app(): express.Express {
  // other configurations
  // 👇 add this line in order to allow the server to read the body of the request
  server.use(express.json());

  // 👇 add this line to enable on-demand revalidation
  server.post(
    '/api/invalidate',
    async (req, res) => await isr.invalidate(req, res)
  );
}

Now, we can invalidate the cache by sending a POST request to the /api/invalidate endpoint. With the below request body:

{
  "token": "your-secret-token",
  "urlsToInvalidate": ["/", "/docs/on-demand-revalidation"]
}

token is the secret token that you set in the ISRHandler invalidateSecretToken field. urlsToInvalidate is an array of URLs that you want to invalidate.

Here's an example of how to invalidate the cache using Postman:

Postman Invalidate Cache

Usecases​

This feature is best used when you have a CMS that updates the data frequently. For example, if you have a blog that you update frequently, you can use on-demand revalidation to invalidate the cache whenever you update a blog post. This way, you won't have to wait for the cache to expire to get the latest data.

tip

By setting the revalidate: 0, you can disable the scheduled (automatic) revalidation. The cache will never revalidate, unless you manually invalidate it using on-demand revalidation.

It's just like when you use changeDetectorRef.detach with changeDetectorRef.detectChanges methods.

You have full control!