Is it possible to receive out-of-order responses with HTTP?

Question

Sec 8.1.2.2 Pipelining says:

\"A server MUST send its responses to requests in the same order that the requests were received\".

Answer 1

They will not be handled synchronously unless the WebServer only has 1 thread to handle the requests which may only happen intentionally (possibly under a dev environment). Most of the time the Web server has hundreds of threads available to process requests as they come in and as 1 request may take longer than another, the responses can come back out of order. This is why it is called A(asynchronous)JAX.

1 request could take a full second to respond, while request 2 and 3 take 25ms to respond, thus the 1st request response comes in after both the 2nd and 3rd requests.

You can force a synchronous cycle but at the cost of everything stopping until the request is returned and processed, (Even JS loading spinners would stop).

See this article on forcing synchronous (SJAX) requests. http://www.hunlock.com/blogs/Snippets:_Synchronous_AJAX