Programming Tutorials

  The release of OCaml 5.0 marked the end of the Global Interpreter Lock (GIL) era, introducing native support for shared-memory parallelism (Domains) and direct-style concurrency via Algebraic Effects. However, this paradigm shift creates a friction point for production engineering. The OCaml ecosystem has spent over a decade building on monadic concurrency libraries, primarily  Lwt  and  Async . These libraries rely on "function coloring"—where asynchronous functions return a specific wrapper type (e.g.,  'a Lwt.t )—infecting the entire call stack. Engineers must now decide: Do we continue paying the "monad tax" with Lwt, or do we migrate to  Eio , the effects-based IO library that promises direct-style syntax, structured concurrency, and parallel scalability? The Root Cause: Monadic Concurrency vs. Effect Handlers To make the right architectural decision, you must understand how the runtime behaves in both scenarios. 1. The Lwt Model (Cooperative Monads)...