I was looking for a production ready implementation that I could easily integrate into my "NIP05.social" backend (Node.js, TypeScript, Microsoft SQL server).
I also wanted NIP-42 support for authentication to only allow registered users onto the relay.
I was not really surprised to find none of the available relay implementations a good match and therefore decided to implement the relay myself.
I checked the relay implementation "Nostream" which is written in TypeScript to get some ideas. A really cool project.