Cacher is the code snippet organizer for pro developers

function my_pantheon_varnish_caching() {
    if ( is_user_logged_in() ) {
        return;
    }
    $age = false;
 
    // Home page: 30 minutes
    if ( is_home() && get_query_var( 'paged' ) < 2 ) {
        $age = 30;
    // Product pages: two hours
    } elseif ( function_exists( 'is_product' ) && is_product() ) {
        $age = 120;
    }
 
    if ( $age !== false ) {
        pantheon_varnish_max_age( $age );
    }
}
 
function pantheon_varnish_max_age( $minutes ) {
    $seconds = absint( $minutes ) * 60;
    header( 'Cache-Control: public, max-age=' . $seconds );
}
 
add_action( 'template_redirect', 'my_pantheon_varnish_caching' );