Practical examples of building OCaml projects using Dune, with the Nix package manager and opam2nix tool.
Install Nix, The Purely Functional Package Manager: https://nixos.org/nix/
In the relevant directory, run nix-build - the derivation will install the executable to the Nix store, where it can be executed...
"GraphQL servers in OCaml" ~ https://github.com/andreas/ocaml-graphql-server
See graphql/
"Sinatra like web toolkit for OCaml" ~ https://github.com/rgrinberg/opium
See opium