Performance of webservice

How can I improve the speed of a webservice? I already removed all but a commit of the main object in the exposed microflow.The (complex) structure is a 3 level invoice (header-detail-moredetail, header-detail2-moredetail2) 1-50 lines. Works fine. The speed is currently 1-2 seconds per call. It seems that logging-in takes a while, Can I replace that with a session key? Can I publish 2 identical webservices? Other hints? Except for more iron. Edit: @Michel how can disable the authentication on a published ws? Anonymous user?
1 answers

One easy gain is to disable the track webservice user login option, this avoids that the webservice users' last login details are updated on each login, which save you a write request. This might be interesting for often firing webservice requests.