a basic example of using transients to cache a database query in WordPress

transient-query-caching.php

<?php 

/**
 * Caches the query for 15 minutes to a transient
 * @param  string $color a meta key
 * @return array $posts an array of post objects
 */
function caching_query_example_function( $color ) {
	$cache_key = 'color-transient-' . $color;

	if ( false === ( $posts = get_transient( $cache_key ) ) ) {
		$posts = get_posts( array(
				'meta_query' => array(
					array(
						'key' => 'color',
						'value' => $color,
						'compare' => 'NOT LIKE', 
					),
				),
		) );

		set_transient( $cache_key, $posts, 900 );
	}

	return $posts;
}