Waldemar’s blog

Some time ago I made a little test comparing web services performance using HTTP GET and POST methods. I used the same script, in the same environment with the same web service. HTTP method was the only difference.

I discovered that POST method is twice much faster than request sent using GET method.
You should also know that request size with GET method can be limited, although RFC2616 says:

The HTTP protocol does not place any a priori limit on the length of
   a URI. Servers MUST be able to handle the URI of any resource they
   serve, and SHOULD be able to handle URIs of unbounded length if they
   provide GET-based forms that could generate such URIs.

So if you are planning some web services performance testing or you want to speed up your tests a little bit before customer demo you should consider POST HTTP method.

General HTTP POST GET performance web services