Atlas 4: Only 2 calls at a time and don't expect any order
Browsers make 2 concurrent AJAX calls at a time to a domain. If
you make 5 AJAX calls, browser is going to make 2 calls first, then
wait for any one of them to complete and then make another call
until all remaining 4 calls are complete. Moreover, you cannot
expect calls to execute in the same order as you make the calls.
Here you see, call 3's response download is quite big and thus
takes longer than Call 5. So, Call 5 actually gets executed before
So, the world of HTTP is unpredictable.