HAProxy is a free, very fast and reliable solution offering high availability, load balancing, and proxying for TCP and HTTP-based applications. It is particularly suited for web sites crawling under very high loads while needing persistence or Layer7 processing. Supporting tens of thousands of connections is clearly realistic with todays hardware. Its mode of operation makes its integration into existing architectures very easy and riskless, while still offering the possibility not to expose fragile web servers to the Net.HAProxy implements an event-driven, single-process model which enables support for very high number of simultaneous connections at very high speeds. Multi-threaded or multi-process models can rarely cope with thousands of connections because of system scheduler limits, memory limits, and lock contention everywhere.Event-driven models do not have these problems because implementing all the tasks in user-space allows a finer resource and time management. The down side is that those programs generally don\'t scale well on multi-processor systems. That\'s the reason why they must be optimized to get the most work done from every CPU cycle.