We don't have instrumentation in production, ie. we spec much more at dev time. But for things you'd validate anyway spec is a good match and probably about as

We don't have instrumentation in production, ie. we spec much more at dev time. But for things you'd validate anyway spec is a good match and probably about as performant as hand-written validation. The only strange use of spec I mentioned is validating db queries. For us updates and deletes are rare enough that perf doesn't matter.