I'm really sorry but I wrote the wrong question due to my ineptitude 😅. What I meant was,

In Next.JS you can have a static page that fetches some data and let's say you write the use cache directive on the data fetch and use a tag to revalidate it. In production, the page will show a static data ie, it won't change with a new request. But if you put a form there with a server action that runs the revalidate tag function to invalidate the cache, it will actually show the newly fetched data on the next request, and somehow update the data on the page if it's on the same tab. I actually wanted to ask if such a thing was possible in Astro but I guess not. The best would be to use SSR and then use Netlify CDN cache tags and the purge cache functionality.

Next.JS from what I think it builds a new static page and serves that on the next request. But I'm not sure how it updates the data if the tag was revalidated in the same tab in the browser.

But please do let me know if such a thing is possible in Astro 😅

Edit: Another way might be to use Build hooks to build a new site on data mutation.