There is Ocsigen (https://en.wikipedia.org/wiki/Ocsigen https://en.wikipedia.org/wiki/Ocsigen) which lets you write OCaml on the front-end and back-end, and is

There is Ocsigen (https://en.wikipedia.org/wiki/Ocsigen https://en.wikipedia.org/wiki/Ocsigen) which lets you write OCaml on the front-end and back-end, and is a fully-featured self-contained server. There is also Opium (https://github.com/rgrinberg/opium https://github.com/rgrinberg/opium) which is a Sinatra-like light-weight web server. Neither has the kind of vast community support like Rails or Django enjoys, and I haven't used them in anger either.