rsnext/docs/api-routes/dynamic-api-routes.md

description
You can add the dynamic routes used for pages to API Routes too. Learn how it works here.

Dynamic API Routes

API routes support dynamic routes, and follow the same file naming rules used for pages.

For example, the API route pages/api/post/[pid].js has the following code:

export default (req, res) => {
  const {
    query: { pid },
  } = req

  res.end(`Post: ${pid}`)
}

Now, a request to /api/post/abc will respond with the text: Post: abc.