[wyager]

While I agree a slow build indicates a problem with their build infra, haskell’s purity and type system do rule out issues with mutable State (presumably there isn’t any in the hot-swapped module) and invalid states (the type system prevents invalid states from being constructed, given the way they have a fixed hot-cold API).

The article describes the hot-swapped module as containing frequently changing business logic, which sounds like it’s something they can probably do via an interface with well-constrained or no mutability.