# Astro, prerendering a single component in a SSR page

> Learn how to prerender a single expensive component inside a server-rendered Astro page, using an Astro 3.4 partial with prerender and partial set to true.

Author: Flavio Copes | Published: 2023-10-30 | Canonical: https://flaviocopes.com/astro-prerendering-a-single-component-in-a-ssr-page/

I had a server-rendered [Astro](https://flaviocopes.com/astro-introduction/) page and I was doing a quite intensive calculation on it. It ran on every page load.

So I used a partial (🆕 in Astro 3.4) and set the `prerender` flag on it:

```javascript
---
export const prerender = true
export const partial = true
---

```

Then I included this partial client-side using HTMX (you could also just use a `fetch()` request and swap some innerHTML too).