Let’s suppose you have a plugin that, for one reason or another, stores its own post metadata in a separate database table called codex_postmeta. One of the ways you can achieve synchronization is to be made aware when a post is deleted so that you can replicate the changes yourself.

add_action( 'admin_init', 'wpdocs_codex_init' );
function wpdocs_codex_init() {
    add_action( 'delete_post', 'wpdocs_codex_sync', 10 );
}

function wpdocs_codex_sync( $pid ) {
    global $wpdb;
    $query = $wpdb->prepare( 'SELECT post_id FROM codex_postmeta WHERE post_id = %d', $pid );
    $var = $wpdb->get_var( $query );
    if ( $var ) {
        $query2 = $wpdb->prepare( 'DELETE FROM codex_postmeta WHERE post_id = %d', $pid );
        $wpdb->query( $query2 );
    }
}