I originally posted this back in May of 2015, but I am back to provide more insight.
(Warning this only applies to Microsoft .NET) unsure about PHP or other web technologies.
Setting the Connection Limit
This section explains how to increase the number of simultaneous connections between
the client and WEBSERVER.
By default (.NET), you can create only two simultaneous connections to an HTTP server.
By increasing the number of connections, you can avoid a backlog of requests during times of
very high transaction volume. Microsoft recommends for the connection limit a value that
is 12 times the number of CPUs. For example, if you have two CPUs, you can set the
connection limit to 24. To determine the optimum setting for your application, make sure to
run performance tests.
Examples
You can increase the number of connections in many ways, for example by using an
application- or server-specific configuration file where you can change the setting for a
single or for all hosts. The examples below describe briefly some of the methods that you
can use to increase connection limits.
When set to a value other than -1, the connectionLimit setting in the client
increases the limit for the host where you are sending the request by executing these
statements on your behalf:
You can set the connection limit by using .NET's tag. In this
example, the connection limit for WEBSERVER's test and production hosts is 12 while the
limit for all other hosts is 2:
ServicePoint sp = ServicePointManager.FindServicePoint(uri);
sp.ConnectionLimit = config.ConnectionLimit;
<system.net>
</system.net>
DefaultConnectionLimit
You can set the connection limit for all hosts to which your application is connected before
a connection is made by using the following line in your start-up code:
ServicePointManager.DefaultConnectionLimit = your_value_here;
References
For more information on these and other methods to increase the connection limits, see
the following Microsoft documentation: Managing Connections in the .Net Framework Developer’s Guide ([url=http://msdn2.microsoft.com/en-us/library/7af54za5.aspx]http://msdn2.microsoft.com/en-us/library/7af54za5.aspx[/url]).
Also note we increase the CPU and RAM raised FTFB from an F to C, but after this change it is now a B.