WordPress: Get the X latest posts with the added benefit of using transients to save it from actually running when not necessary.

transient_query.php

<?php

/**
 *
 * Get a potentially cached version of a WP_Query
 *
 * @param int $how_many Optional. How many posts to return.
 * @return WP_Query
 */
function get_transient_query($how_many = 10) {

    // Dynamically create the transient name based on number of $how_many
    $transient_name = 'transient_query_' . $how_many;

    // Try to get the transient
    $transient_query = get_transient($transient_name);

    // Aw shucks, the transient isn't there or is expired
    if (false == $transient_query) {

        // Prep our $args
        $args = array(
            post_status => 'published',
            posts_per_page => $how_many,
        );

        // Instantiate a new WP_Query
        $transient_query = new WP_Query($args);

        // save it as a new transient / update the existing, expired transient
        set_transient($transient_name, $transient_query, 1 * HOUR_IN_SECONDS);
    }

    /*
     * either it was already stored as a transient and we're simplyu returning it
     * or we're returning a freshly stored copy of the query
     */
    return $transient_query;
}