Simultaneous execution of many requests - php

Question

I have an Instagram robot site
My program for each user makes a task that must be run every minute
Now my server has encountered a problem
I want my plan to be optimized
i am 427 user and my script for user create one cron jobs and repeat every minutes
all cron jobs send this formats
mysite.com/api/cron/[userpagename]
and my functions cron this code
/****************************************/
/* CRON */
/****************************************/
public function cron($type = ""){
$schedule_list = $this->db->select('activities.*, account.username, account.password, account.proxy, account.default_proxy')
->from($this->tb_activities." as activities")
->join($this->tb_accounts." as account", "activities.account = account.id")
->where("account.username = '{$type}' AND activities.status = 1 AND activities.time <= '".NOW."' AND account.status = 1")->order_by("time", "asc")->limit(2,0)->get()->result();
if(!empty($schedule_list)){
foreach ($schedule_list as $key => $schedule) {
if(!permission("instagram/activity", $schedule->uid)){
$this->db->delete($this->tb_activities, array("id" => $schedule->id));
$this->db->update($this->tb_activities, array("status" => 0, array("id" => $pid)));
$this->db->delete('instagram_activities_log', "uid = '{$schedule->uid}'");
$this->db->delete('instagram_activities', "uid = '{$schedule->uid}'");
$this->db->delete('instagram_accounts', "uid = '{$schedule->uid}'");
$this->deleteLineInFile("./cron.txt",$schedule->username);
exec('crontab ./cron.txt');
$this->model->send_email(get_option("email_renewal_reminders_subject", ""), get_option("email_renewal_reminders_content", ""), $schedule->uid);
}
$action = $schedule->action;
echo $schedule->action;
$mainId = $schedule->pid;
$settings = json_decode($schedule->data);
$speed = get_value($settings, "speed");
$next = get_time_next_schedule($schedule->settings, $speed->$action);
$stop = $this->stop_activity($mainId, $schedule->action , $schedule);
print_r(get_random_numbers(20));
if($stop){ break; }
if($next->task != 0){
$schedule->number = $next->task;
$proxy_data = get_proxy($this->tb_accounts, $schedule->proxy, $schedule);
try {
$ig = new InstagramAPI($schedule->username, $schedule->password, $proxy_data->use);
$result = $ig->activity->process($schedule);
//print_r($result);
if(is_array($result) || is_object($result)){
$this->save_log($schedule, $result);
$next->numbers = get_action_left($next->numbers, $result, $next->task);
}
} catch (Exception $e) {
print_r($e->getMessage());
$mess = Instagram_Get_Message($e->getMessage());
//ig_update_setting($schedule->action."_block", $e->getMessage(), $mainId);
if(strpos($mess, "This action was blocked")){
$next->numbers = get_random_numbers(0);
ig_update_setting($schedule->action."_block", "", $mainId);
}
else{
$next->numbers = get_action_left($next->numbers, array(), $next->task);
}
}
}
$this->db->update(INSTAGRAM_ACTIVITIES, array(
"time" => date("Y-m-d H:i:s", strtotime(NOW) + $next->minute*60),
"settings" => json_encode($next->numbers),
"changed" => date("Y-m-d H:i:s", strtotime(NOW) + $next->minute*60)
),
array("id" => $schedule->id)
);
}
}else{
echo "No activity";
}
I want to send all these requests together without error or failure