// Disable SQL_CALC_FOUND_ROWS for pagination
add_filter('found_posts_query', function($sql){
    return preg_replace('/SQL_CALC_FOUND_ROWS/i', '', $sql);
});

// Custom fast COUNT(*) for pagination
add_filter('found_posts', function($found_posts, $query){
    global $wpdb;

    if (!$query->is_main_query() || !$query->is_archive() && !$query->is_home()) {
        return $found_posts;
    }

    $cache_key = 'fast_count_' . md5($query->request);
    $cached = wp_cache_get($cache_key, 'fast_query');

    if ($cached !== false) {
        return $cached;
    }

    // Convert main query to COUNT(*)
    $count_query = "SELECT COUNT(*) FROM ({$query->request}) AS t";
    $total = (int) $wpdb->get_var($count_query);

    // Cache for 5 minutes
    wp_cache_set($cache_key, $total, 'fast_query', 300);

    return $total;
}, 10, 2);