Hello,
I try to sort events custom post type by start timestamp, but it doesn’t work

function get_events($event_types=null, $periode=null, $posts_per_page=-1) {

    $type_args = array();
    if($event_types) {
        $type_args = array(
            'key' => 'event_type',
            'compare' => 'IN',
            'value' => $event_types,
        );
    }

    $past_args = array(
        'key' => 'event_fin_timestamp',
        'compare' => '<',
        'value' => strtotime(date("Y-m-d")),
    );

    $present_args =  array(
        'relation' => 'AND',
        array(
            'key' => 'event_debut_timestamp',
            'compare' => '<=',
            'value' => strtotime(date("Y-m-d")),
        ),
        array(
            'key' => 'event_fin_timestamp',
            'compare' => '>=',
            'value' => strtotime(date("Y-m-d")),
        ),
    );

    $future_args = array(
        'key' => 'event_debut_timestamp',
        'compare' => '>',
        'value' => strtotime(date("Y-m-d")),
    );

    $periode_args = array();
    if($periode) {
        if($periode == 'past') $periode_args = $past_args;
        if($periode == 'present') $periode_args = $present_args;
        if($periode == 'future') $periode_args = $future_args;
    }
    
    $events_query = new WP_query(
        array(
            'post_type' => 'event',
            'posts_per_page' => $posts_per_page,
            'order_by' => 'meta_value',
            'meta_key' => 'event_debut_timestamp',
            'order' => 'ASC',
            'meta_query' => array(
                $type_args,
                $periode_args
            )
        )
    );
    return $events_query->posts;

}

Anyone could help me, or send me a link about this subject ?
Thank you, and sorry for my poor english :/