Drupal Gotcha : Cache_get() Returns Expired Items

cache_get.php

cache_get() returns $cache objects even if the cached item is stale (expired)

function custom_fn_get_data() {
  // Return the cached data
  $cache = cache_get('custom:fn_get_data');
  if (!$cache) {
    // Some expensive processing to build the data.
    $data = complicated_recursion_and_loops_on_lots_of_data();
    
    // Cache the data and rebuild it every hour
    $expire = time() + (60 * 60);
    cache_set('custom:fn_get_data', $data, 'cache', $expire);
  }
  else {
    $data = $cache->data;
  }
  return $data;
}

You can make it better by this way

 if (!$cache or time() > $cache->expire) {