Код:
function show_random_posts_optimized($count = 3) {
$args = array(
'numberposts' => -1,
'fields' => 'ids',
'post_type' => 'any',
);
$random_posts_ids = get_posts($args);
$rnd_posts = array_rand($random_posts_ids, $count);
foreach ( $rnd_posts as $post_index ) {
$id = (int)$random_posts_ids[$post_index];
$post = get_post($id);
echo '<p><a href="'.get_permalink($post->ID).'">'.$post->post_title.'</a></p>';
}
}