When you load a dump for development, records may reference images that are not available on your machine.

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Requests to those images may end up on your application, e.g. if a catch-all route is defined that leads to a controller doing some heavy lifting. On pages with lots of missing images, this slows down development response times.

You can fix that by defining a Rails route like this:

if Rails.env.development?
  scope format: true, constraints: { format: /jpg|png|gif/ } do
    get '/*anything', to: proc { [404, {}, ['']] }
  end
end

Images are (usually) served directly from public or assets and won't hit your controllers/routes, as long as the files exist. If files are missing, the request will be handled by the above route which instantly responds with an empty HTTP 404 response.