I found this interesting tidbit on the HAProxy page: Keep-alive was invented to reduce CPU usage on servers when CPUs were 100 times slower. But what is not sa

I found this interesting tidbit on the HAProxy page: Keep-alive was invented to reduce CPU usage on servers when CPUs were 100 times slower. But what is not said is that persistent connections consume a lot of memory while not being usable by anybody except the client who openned them. Today in 2009, CPUs are very cheap and memory is still limited to a few gigabytes by the architecture or the price. If a site needs keep-alive, there is a real problem. Highly loaded sites often disable keep-alive to support the maximum number of simultaneous clients. The real downside of not having keep-alive is a slightly increased latency to fetch objects. Browsers double the number of concurrent connections on non-keepalive sites to compensate for this. Don't know if it's true or not, but it doesn't take much thought to realize if someone wanted to DDOS a server they would use persistent connections.