wordpress-transient-caching.php

<?php 
/**
 * Setup wp_query arguments for the loop. Cache the results for 4 hours.
 *
 * @link http://codex.wordpress.org/Transients_API
 */

// Check for transient
if ( ! ( $my_query = get_transient( 'foo_featured_posts' ) ) ) {
	
	// If transient isn't set, execute WP_Query
	$my_query = new WP_Query(
		array(
			'category'		=> 'featured',
			'posts_per_page'	=> 5
		)
	);

	// Create transient and expire after 4 hours
	set_transient( 'foo_featured_posts', $my_query, 4 * HOUR_IN_SECONDS );
}

/**
 * Run the loop.
 * 
 * @link http://codex.wordpress.org/The_Loop
 */
if ( $my_query->have_posts() ) :
	while ( $my_query->have_posts() ) : $my_query->the_post(); ?>
		
		<!-- Do stuff -->

	<?php endwhile; else : ?>
		<p>Sorry, no posts found</p>
<?php endif; wp_reset_postdata(); ?>