Exporting a function called getServerSideProps.

When exporting a function called getServerSideProps (Server-Side Rendering) from a page, Next.js will pre-render this page on each request using the data returned by getServerSideProps. This is useful if you want to fetch data that changes often, and have the page update to show the most current data.

export async function getServerSideProps() {
  // Fetch data from external API
  const res = await fetch('https://api.github.com/repos/vercel/next.js')
  const repo = await res.json()
  // Pass data to the page via props
  return { props: { repo } }
}
 
export default function Page({ repo }) {
  return (
    <main>
      <p>{repo.stargazers_count}</p>
    </main>
  )
}

You can import modules in top-level scope for use in getServerSideProps. Imports used will not be bundled for the client-side. This means you can write server-side code directly in getServerSideProps, including fetching data from your database.