I convinced the company I work at to use Haskell for REST services. The technical leadership team was already interested improving the reliability and rigor of

I convinced the company I work at to use Haskell for REST services. The technical leadership team was already interested improving the reliability and rigor of our web backend, but weren't thinking about exploring other programming languages. (we primarily use PHP) I knew Haskell would be hard to sell, but I also had concerns about it myself, so I ran a live-fire test: In my spare time, I wrote an interface-compatible Haskell implementation of a particular service that drove a lot of load, but was noncritical. I load-tested this service by flipping an nginx switch to divert traffic to the Haskell implementation. Leadership was ok with this because we could just flip the switch back if there were any issues: The risk of customer impact was miniscule. After some initial tests, we left it to run for a few months without manual intervention. Over the course of this side-project, I got a few curious coworkers to learn Haskell to help out. When the right project came along, leadership still had concerns, but I had lot of hard evidence to show that Haskell superbly fit our technical requirements and that the nontechnical problems (like hiring and training) were probably surmountable.