Drupal 8 - Stock quote cache
Put this in a custom module:


/**
 * Implements hook_block_view_alter().
 */
function MYMODULE_block_view_alter(array &$build, Drupal\Core\Block\BlockPluginInterface $block) {
  if (!empty($build['#id']) && $build['#id'] == 'stocktickerblock') {
    $build['#cache']['max-age'] = 0;
  }
}


but if the your 'stocktickerblock' block is from a custom plugin you can set the build cache directly in that plugin render array.