HAProxy

HAProxy is free, open source software that provides a high availability load balancer and proxy server for TCP and HTTP-based applications that spreads requests across multiple servers. It is written in C and has a reputation for being fast and efficient (in terms of processor and memory usage).
HAProxy is used by a number of high-profile websites including GoDaddy, GitHub, Bitbucket, Stack Overflow, Reddit, Slack, Speedtest.net, Tumblr, Twitter and Tuenti and is used in the OpsWorks product from Amazon Web Services.
History.
HAProxy was written in 2000 by Willy Tarreau, a core contributor to the Linux kernel, who still maintains the project.
In 2013, the company HAProxy Technologies, LLC was created to continue developing the software in addition to contributions from the open-source community. The company provides a commercial offering, HAProxy Enterprise and appliance-based application-delivery controllers named ALOHA. The company provides technical support and additional modules that extend the functionality of HAProxy.
Features.
HAProxy has the following features:
HAProxy Community vs HAProxy Enterprise.
HAProxy Enterprise Edition is an enterprise-class version of HAProxy that includes enterprise suite of add-ons, expert support, and professional services. At its core, it incorporates feature backports from the HAProxy development branch for customers who require immediate access to the latest functionality in a hardened version of code.
ALOHA.
HAProxy Technologies’ ALOHA is a plug-and-play load-balancing appliance that can be deployed in any environment. ALOHA provides a graphical interface and a templating system that can be used to deploy and configure the appliance. Its main intention is to be a direct competitor to hardware load balancing boxes/appliances to companies that still provide separate appliance load balancers, such as F5 Networks.
Versions.
HAProxy has had the following version releases:
Performance.
Servers equipped with 6 to 8 cores generally achieve between 200000 and 500000 requests per second, and have no trouble saturating a 25 Gbit/sec connection under Linux. 64-core ARM servers were shown to reach 2 million requests per second and 100 Gbps.