&quot;Apache, due to its process model.&quot;... &quot;(prefork)&quot;<p>Seems to me that the above is all based on reflections from decades ago w&#x2F; Apache httpd 1.3. Right now, all web servers can handle similar levels of concurrency with the bottleneck being the network pipe itself.<p>ATS is a great platform; using it in combo w&#x2F; Apache httpd (2.4) allows a pure open source implementation with all the power, speed, reliability one could want, and protection against Open Core business models.