A Couple Million Lines of Haskell: Production Engineering at Mercury | Hacker News

Mercury’s engineering post says its roughly 2-million-line Haskell codebase helps enforce correctness in production through strong types and type-driven design.

The discussion highlighted built-in observability, including custom clients for tracing, timeouts, and other production controls.

Supporters pointed to Haskell’s safety benefits in finance and services where bugs are costly, and noted comparisons with Rust and TypeScript.

Critics and practitioners also called out real tradeoffs: slow builds, harder cross-compilation, static linking, and added deployment complexity.