File: vendor/wp-coding-standards/wpcs/WordPress/Docs/WP/CronIntervalStandard.xml

<documentation title="Cron interval">
    <standard>
    <![CDATA[
    Cron schedules running more often than once every 15 minutes are discouraged. Crons running that frequently can negatively impact the performance of a site.
    ]]>
    </standard>
    <code_comparison>
        <code title="Valid: Cron schedule is created to run once every hour.">
        <![CDATA[
function adjust_schedules( $schedules ) {
    $schedules['every_hour'] = array(
        'interval' => <em>HOUR_IN_SECONDS</em>,
        'display'  => __( 'Every hour' )
    );
    return $schedules;
} 

add_filter( 
    'cron_schedules', 
    'adjust_schedules'
); 
        ]]>
        </code>
        <code title="Invalid: Cron schedule is added to run more than once per 15 minutes.">
        <![CDATA[
function adjust_schedules( $schedules ) {
    $schedules['every_9_mins'] = array(
        'interval' => <em>9 * 60</em>,
        'display'  => __( 'Every 9 minutes' )
    );
    return $schedules;
} 

add_filter( 
    'cron_schedules', 
    'adjust_schedules'
);
        ]]>
        </code>
    </code_comparison>
</documentation>