If in doubt, use "tc" to do traffic shaping (on Linux) or SeriousBit's NetBalancer (on Windows). http://www.cyberciti.biz/faq/linux-traffic-shaping-using-tc-...

I regularly test my websites with various tc settings, including traffic shaping, packet loss, line outages etc. Lots of manual work, but it really helps to see which parts of your API can be traffic-optimized.