Immutability is a very powerful idea when record keeping and dealing with transactions. I know of at least one major bank whose ledgers are written Haskell.
Sounds like a broken hiring process right there. Anything you care to share about why that didn't work out? I can't imagine a company having an opportunity to hire you and choosing not to.
I don't mind sharing about that. Standard Charter has the reputation for being a great Haskell shop and I have been trying for years to up my Haskell skills.
I simply didn't have enough background in Haskell. The interview was fun. The interviewer did his PhD in Haskell and compiler theory.
Around the same time, I applied to Facebook's Haskell group, and I got to interview with Simon Marlow, which was great. He also said that I didn't have enough Haskell experience and suggested that I do more Haskell consulting work, and re-apply in a year.
Anyway, I love coding in Haskell but my skills need improvement.
It's Walmart and not a financial institution but this is a great talk about immutability applied to the backend services using F#: https://youtu.be/FskIb9SariI
Coincidentally, Walmart also maintains a lot of clojure libraries now, including the go-to graphql implementation in clojure: https://github.com/walmartlabs/lacinia
