Don Stewart, co-author of Real World Haskell and author of many Haskell Stack Overflow answers, joins us to discuss working with Haskell at large scale: how to organize, deploy, and test more than 1 million lines of Haskell code. He also shares some insights on hiring, training, and working with a large team of Haskell developers. To start the episode, we discuss performance and optimization of Haskell programs.