This document provides an overview of deploying Ruby on Rails applications. It discusses the evolution of different web servers and technologies used over time, including CGI, Apache with various modules, Lighttpd, and others. It introduces Mongrel as a fast HTTP server library and explains how its use requires clustering to scale Rails applications across multiple processes. The document then covers tools for load balancing and proxying to Mongrel clusters, including Nginx which provides high performance. It also describes an event-driven version of Mongrel called Swiftiply that improves throughput. Overall it presents best practices and optimizations for deploying scalable and high performing Rails applications.