@queicherius Thanks for the PR. Seems there's an error in the test case. I'll check this later.

I was testing this change a bit more since I opened the PR and I feel like since the headers depend on the application it would be good to have a configuration option for this.

I could implement an extension to rules like this (tho it would not work for rules as a function without a breaking change):

  rules: [
    { url: '^/_next/static/.*', ttl: 60 * 60, cacheControl: 'public, max-age=31536000, immutable' },
    { url: '.*', ttl: 5 * 60, cacheControl: 'public, max-age=0, s-maxage=300, stale-while-revalidate' },
  ],

or a function:

  cacheControl: (req, ttl) => {
    if (req.url.startsWith('/_next/static')) {
      return 'public, max-age=31536000, immutable'
    }

    return `public, max-age=0, s-maxage=${ttl}, stale-while-revalidate`
  },

Which would you prefer?

I've updated the implementation with the second option (the cacheControl configuration option). Let me know if you're happy with that, and then I'll update tests & docs 👍

What happens if getServerSideProps sets its own cache control header? Can't we just pass that along? That's where we're implementing our own stale-while-revalidate settings