Senior & Lead Engineer
Interview Mastery Hub

The Golden Rule: Never call external network APIs inside a database transaction

Use DB::afterCommit() callbacks:

DB::transaction(function () use ($order, $paymentData) {
    $order->update(['status' => 'paid']);
    PaymentTransaction::create([...]);

    // Dispatch side-effects ONLY after database commit succeeds
    DB::afterCommit(function () use ($order) {
        SendInvoiceEmailJob::dispatch($order);
        NotifyThirdPartyFulfillment::dispatch($order);
    });
});

Implementing CastsAttributes

class MoneyCast implements CastsAttributes
{
    public function get(Model $model, string $key, mixed $value, array $attributes): ?Money
    {
        return $value !== null ? new Money((int) $value, $attributes['currency'] ?? 'USD') : null;
    }

    public function set(Model $model, string $key, mixed $value, array $attributes): array
    {
        if ($value instanceof Money) {
            return [$key => $value->getAmountInCents(), 'currency' => $value->getCurrency()];
        }
        return [$key => (int) $value];
    }
}

Using DB::whenQueryingForLongerThan

In AppServiceProvider::boot():

DB::whenQueryingForLongerThan(500, function (Connection $connection) {
    Log::warning("Database query exceeded 500ms on [{$connection->getName()}]");
    // Send alert to Sentry or Slack webhook
});

Dynamic Rate Limiter in AppServiceProvider

RateLimiter::for('api', function (Request $request) {
    $user = $request->user();
    if (! $user) {
        return Limit::perMinute(30)->by($request->ip());
    }

    return match ($user->subscription_tier) {
        'enterprise' => Limit::perMinute(10000)->by($user->id),
        'pro' => Limit::perMinute(1000)->by($user->id),
        default => Limit::perMinute(60)->by($user->id),
    };
});

Graceful Termination Workflow

1. Catch SIGTERM in worker: In Kubernetes, set terminationGracePeriodSeconds: 120.
2. Supervisor Configuration: Set stopwaitsecs = 120 so Supervisor gives workers up to 2 minutes to finish processing current job before force killing (SIGKILL).
3. Queue Worker Command:

   php artisan queue:work --stop-when-empty --max-time=3600 --timeout=90