“In the AJAX world, a client can make a request, the server responds that it has received the request (so the client can get on with something else), and then at some random time later the actual response to the original request is returned. You see the problem? It becomes a challenge to match requests with the correct responses. From a programming standpoint, the performance tool must spawn a thread that waits for thecorrect response while the rest of the script continues to execute. A deft scripter may
be able to code around this, but it may require signifcant changes to a script with the
accompanying headache of ongoing maintenance. The reality is that not all testers are bored developers, so it’s better for the performance tool to handle this automatically.”