Multiple XHR requests are slow
<p>I've created an Angular.js application that issues multiple XHR requests to a PHP application built with Yii framework. Problem is that it seems like that the multiple requests slow down each other - but I don't know why. Please see this image from Google Chrome developer tools:</p>

<p><a href="https://i.stack.imgur.com/hcF4H.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/hcF4H.png" alt="enter image description here"></a></p>

<p>It is okay that the last three requests wait for a few milli seconds. This is because Chrome allows only six concurrent requests. My problem is e.g. that request 8, 9 and 10 takes 6-8 seconds. When I copy the URL of these requests and open them one by one in my browser, they only take &lt; 800ms. How could this possibly be? Is this a problem located in Apache or a client issue? How can I track this down easily?</p>