curl -I url -H 'Cache-Purge: 1'

Thing.where.not(image: nil).find_each do |e|
  %i(large small).each do |v|
    url = URI.parse(e.image.send(v).url)
    req = Net::HTTP::Get.new(url.path)
    req.add_field("Cache-Purge", "1")
    res = Net::HTTP.new(url.host, url.port).start do |http|
      http.request(req)
    end
  end
end