module I18n::Backend::CacheFile

def load_file(filename)

and skip loading the file if its contents are still up-to-date.
Track loaded translation files in the `i18n.load_file` scope, 
def load_file(filename)
  initialized = !respond_to?(:initialized?) || initialized?
  key = I18n::Backend::Flatten.escape_default_separator(normalized_path(filename))
  old_mtime, old_digest = initialized && lookup(:i18n, key, :load_file)
  return if (mtime = File.mtime(filename).to_i) == old_mtime ||
            (digest = OpenSSL::Digest::SHA256.file(filename).hexdigest) == old_digest
  super
  store_translations(:i18n, load_file: { key => [mtime, digest] })
end