serve-brotli.js

const path = require('path')
const { readFileSync } = require('fs')

exports.handler = async function http (req) {
  let here = path.dirname('.')

  let postsFilePath = path.join(here, 'rss.xml.br')
  let posts = readFileSync(postsFilePath, 'binary')
  console.log(posts.length)

  let b64 = Buffer.from(posts).toString('base64')
  console.log(b64.length)

  return {
    statusCode: 200,
    headers: {
      'cache-control': 'max-age=86400',
      'content-type': 'application/rss+xml',
      'content-encoding': 'br',
      'content-length': b64.length
    },
    body: b64,
    isBase64Encoded: true,
  }
}