How to make mysql process requests one by one in laravel 5.5?

Question

MySQL

The problem is the following.
The site can have 2-3 requests per second from one user.
There is a balance in the database, when he presses the pay button simultaneously with a millisecond, it is debited only 1 time, since the site or database does not have time to process this request, it goes at the same time.
At the moment I do so, do not judge strictly this is my first experience with the balance.
$this->user->money - $amount
$this->user->save();
Is it possible to somehow force the site to process requests to change balances in turn?
Thanks in advance for your reply.

Answer 1

And this is solved ... drum roll ... in bursts! Rabbitmq, Kafka and more. By the way, Keeping the balance directly in the user is a bad idea.
And if you think carefully, then you need to read about idempotent operations and not withdraw money from the account, but create a transaction initially and close it, Ama background, asynchronously, recalculate the balance

Answer 2

Open a transaction, pull out a user with a lock ->lockForUpdate(), perform your manipulations / checks, save, commit the transaction.

DB::transaction(function () use (&$user) {
    $user = User::whereKey($user->getKey())->lockForUpdate()->firstOrFail();
    if ($user->balance) // blabla
    $user->balance -= 100;
    $user->save();
});

Nothing more is needed.