MacBook Air 2015 is a bit slow booting up I got my Mac restored completely yesterday by some guy at the Apple Store.
It runs the latest version of El Capitan now, however, when I turn it on, it takes a little longer to load the OS than it did before.

It is not really that big of a deal, since heavier applications like Xcode (involving Simulator), Photoshop and smaller ones like Safari, iTunes or Maps work just like they used to. It turns off and goes to sleep right away, the only issue is when it launches the whole OS, the Apple logo with the loading bar is on for a bit too long.

The guy at the Apple Store said if I am bothered with this ('cause it would bother him, he said), I should take it to a full checkup. This Mac is my workstation and 1,5 weeks in service is not really going to happen anytime soon.

Are there any ways to work around this problem and any tips what might cause this? The reason why it was restored is because I was reinstalling the OS, however, my internet connection broke at some point. El Capitan had been uninstalled, but the new version hasn't been downloaded yet. So I was like I better take it to the store then mess everything up by myself.

Before I used 10.11.0, now it is 10.11.5.
I have to say that each version of El Capitan (including 10.11.0) slowed a little more my MacBook Air. 
In Yosemite the boot was easily 3 times faster.

Those days, it's the normal behavior of new system versions...