The broader tech community often views functional programming (FP) as a beautiful, purely academic exercise-great for category theory and Type-Driven Development, but perhaps too abstract for the grit of high-throughput production backends.
That assumption is wrong.
When faced with optimizing the core transaction engine on the CRED backend, we used PureScript and Haskell to dismantle a legacy architecture, driving latency down from a grueling 60 seconds to a crisp 6 seconds-a 90% performance gain.
This wasn’t achieved by upgrading hardware or tweaking thread pools. It was achieved by leveraging the fundamental primitives of functional programming: the Aff monad for high-performance non-blocking I/O, and an algebraic data type (ADT) driven Domain-Specific Language (DSL) to guarantee transactional safety.
Here is the engineering case study of how we did it.
