We have an ASP.NET MVC application + IIS 7.5 + SQL Server 2008 R2.

We have to load a lot of aggregate counters on the each page. We decided to use ajax and call with javascript for each counter or groups of counters and return them as JSON result.

We solve the problem that user doesn't wait for page loading, page loads fast. User waits for counters loading while seeing other page content.

But we thought that if we make calls from javascript - our queries will be make async, but we notice, that it is not. All our javascipt calls runs immediately, but action that they invoke are in queue.

If we use Async Controller ability - all counters calculating simultaneously, but user has to wait for the longest counter calculating before page loads.

The question:
We want to understand what is happens if we use ajax and call two or more actions simultaneously. And how can we configuring this. (also in each action we make some queries to sql server)