protected function generate_cache_key( array $args, $sql ) {
    global $wpdb;

    // Replace wpdb placeholder in the SQL statement used by the cache key.
    $sql = $wpdb->remove_placeholder_escape( $sql );

    $key          = md5( $sql );
    $last_changed = wp_cache_get_last_changed( 'users' );

    if ( empty( $args['orderby'] ) ) {
      // Default order is by 'user_login'.
      $ordersby = array( 'user_login' => '' );
    } elseif ( is_array( $args['orderby'] ) ) {
      $ordersby = $args['orderby'];
    } else {
      // 'orderby' values may be a comma- or space-separated list.
      $ordersby = preg_split( '/[,\s]+/', $args['orderby'] );
    }

    $blog_id = 0;
    if ( isset( $args['blog_id'] ) ) {
      $blog_id = absint( $args['blog_id'] );
    }

    if ( $args['has_published_posts'] || in_array( 'post_count', $ordersby, true ) ) {
      $switch = $blog_id && get_current_blog_id() !== $blog_id;
      if ( $switch ) {
        switch_to_blog( $blog_id );
      }

      $last_changed .= wp_cache_get_last_changed( 'posts' );

      if ( $switch ) {
        restore_current_blog();
      }
    }

    return "get_users:$key:$last_changed";
  }