I use the Refined library for scala and it works incredibly well (a few bumps here or there, and some occasional boilerplate for library interop). On my app ser

I use the Refined library for scala and it works incredibly well (a few bumps here or there, and some occasional boilerplate for library interop). On my app server, it basically becomes my validation layer for all request data, after which I only worry about object ownership/authorization. The big win with refined types is from compiler level support though. With relatively simple checking occurring mostly at IO boundaries, you can eliminate or make obsolete massive portions of testing, type checking, manual optimization, etc., and enable massive amounts of automated optimization. In other words, the "too expensive" refinement checking at runtime becomes a net performance and engineering benefit over the whole product lifecycle.