iRule/Reverse Proxy configuration

To send a specific URL to another server is a piece of cake with an iRule, create a separate pool where the member is the cloud server and then use something like this:

when HTTP_REQUEST {
   if { [HTTP::uri] starts_with "/en-us/blog/top-quartile" }{
      pool cloud-server-pool
   }
}

SNAT is going to be important as well, so either use SNAT on the Virtual Server for all traffic or you could enable SNAT in above iRule if only that traffic should be SNAT:ed.