Awesome article, thanks for the upload! I'm having some problems following the "Transform io-ts error towards a more standard error response" section. Would you mind sharing what version of io-ts you are using?
That's cool, I'm personally in the same Italian slack channel with Giulio but he deploys new releases so often that's hard even for me to follow all the updates :D
Thanks for reporting, I may add a note later in the article
The T generic in const validator: <T>(decoder: Decoder<T>) => RequestHandler<ParamsDictionary, any, T> is what makes the decoded value strictly typed. In any case just check express types to understand how the generics are passed in the flow