A COUPLE MILLION LINES OF HASKELL: PRODUCTION ENGINEERING AT MERCURY

Summary from the TLDR Dev newsletter

Mercury's successful operation of a two-million-line Haskell codebase in fintech shows the language's viability at scale despite a team largely new to the language. Haskell has an ability to encode important operational knowledge and institutional memory directly into type-safe interfaces, making the "right thing easy." They treat purity as a boundary, design for introspection with records of functions, and use types for critical invariants.