Yii2.0 RESTful API的速度限制是什么？有什么用？

php yii migrate/create add_allowance_and_allowance_updated_at_to_user

/**
 * {@inheritdoc}
 */
public function safeUp()
{
    $this->addColumn('user', 'allowance', $this->integer());
    $this->addColumn('user', 'allowance_updated_at', $this->integer());
}

/**
 * {@inheritdoc}
 */
public function safeDown()
{
    $this->dropColumn('user', 'allowance');
    $this->dropColumn('user', 'allowance_updated_at');
}

php yii migrate

namespace api\models;

use Yii;
use yii\base\NotSupportedException;
use yii\behaviors\TimestampBehavior;
use yii\db\ActiveRecord;
use yii\filters\RateLimitInterface;
use yii\web\IdentityInterface;

class User extends ActiveRecord implements IdentityInterface,RateLimitInterface
{
    .
    .
    .
}

public function getRateLimit($request, $action)
{
    return [1, 1]; // $rateLimit requests per second
}

public function loadAllowance($request, $action)
{
    return [$this->allowance, $this->allowance_updated_at];
}

public function saveAllowance($request, $action, $allowance, $timestamp)
{
    $this->allowance = $allowance;
    $this->allowance_updated_at = $timestamp;
    $this->save();
}

use yii\filters\auth\CompositeAuth;
use yii\filters\auth\HttpBearerAuth;
use yii\filters\auth\QueryParamAuth;
use yii\filters\RateLimiter;

public function behaviors()
{
    $behaviors = parent::behaviors();
    $behaviors['rateLimiter'] = [
        'class' => RateLimiter::className(),
        'enableRateLimitHeaders' => true,
    ];
    $behaviors['authenticator'] = [
        'class' => CompositeAuth::className(),
        'authMethods' => [
            //Http::className(),
            HttpBearerAuth::className(),
            QueryParamAuth::className(),
        ],
    ];
    //$behaviors['rateLimiter']['enableRateLimitHeaders'] = true;
    return $behaviors;
}