Spray VS Http4s

I purchased the very entertaining book Seven Languages in Seven Weeks. Although I found Haskell fascinating and tempting, I knew it was unrealistic to introduce it in our company. Scala on the other hand looked like it could be the holy grail: All the characteristics I was looking for, no need to abandon the JVM and its cornucopia of tools and libraries, and the possibility for coexistence with Java and therefore incremental adoption. After implementing some simple programs to identify any immediate risks of committing to the language and its ecosystem, I started to introduce Scala in customer projects. Luckily, I was fortunate enough to work with open-minded, curious, and ambitious team members who were also experienced enough to appreciate the benefits of the language. We immediately applied our experience with functional programming, and embraced immutability. Libraries like Slick and Akka HTTP (we actually started out with its predecessor, Spray) made building database-backed REST services a breeze. And the resulting code was robust and highly maintainable. Scala's expressive type system and type inference made it easy to build a restrictive, consistent domain model without bloating the code. There was virtually no overhead. Any boilerplate could be easily abstracted out. In the end, the application code felt natural, concise and elegant. Programming was fun again.

There are functional frameworks: https://http4s.org/

If you look at the example it is listed as an import but there is no explicit reference to it. And if you were just doing basic synchronous responses then that would be the only time you would see it.

If you want something more powerful, pure-functional and you need to do complex, concurrency-heavy operations, have a look at http4s: https://http4s.org/

I don't think this is toxic but still, it doesn't sit well with me: https://github.com/http4s/http4s/issues/4718

http4s

Here is a possible sketch with the functional http4s library. In http4s, both Http clients and servers are modelled as functions from Http requests to an Http response generated from an IO action. This would be like a function Request => IO[Response], which in http4s is called an HttpApp.

Http4s: https://http4s.org/

Have you checked http4s? I'm using it as a lightweight HTTP server with routing, etc. It might be not your cup of tea, if you don't use pure functional programming, etc, though.