interop-cats VS ZIO

If you're using http4s, don't use ZIO. Yes, ZIO has an interop-cats module, so you can do this. But using http4s means you're working in the conceptual framework the Typelevel ecosystem is based on (and what interop-cats does can be characterized as "describe ZIO's implementation in those terms, so the Typelevel ecosystem can make heads or tails of it.") This is essentially all cost and no benefit: you can't avoid understanding the Typelevel ecosystem if you use http4s (at least, no more than you can by using cats-effect), and you don't get any of the value proposition of ZIO (interop-cats gives you Typelevel typeclass instances for the RIO type alias, which means your error channel is rooted in Throwable, and you're faced with the most complex part of the ZIO ecosystem: ZLayer, which the Typelevel ecosystem doesn't use and doesn't need). Finally the ZIO ecosystem is still quite immature, and this brings us to documentation. There is not (yet!) anything comparable to:

These are necessarily oversimplifications. In particular, the ZIO ecosystem offers the relevant instances of cats-effect typeclasses to support use of the ZIO type in the cats-effect ecosystem.

However, ZIO continues to offer cats-effect type classes and I certainly have no doubt cats-effect 3 continues to benefit from John's contributions. Furthermore, I likewise don't doubt the value of the ZIO ecosystem generally, and John's success in building the ZIO community speaks for itself. I personally have chosen to remain closer to the other, let's say "classical," pure FP ecosystems, partially for historical (or, if you prefer, "sunk cost") reasons, but partially because I'm satisfied the value of the Haskell/Typelevel/PureScript/fp-ts/etc. interplay warrants it.

It seems that zio/interop-cats faces a similar issue.

scala has 2 healthy and pretty complete lib ecosystems : check out typelevel and ZIO. Both are FP oriented, which might not be your cup of tea at first glance but I would encourage you to try em out ! Softest introduction would be to start with the typelevel cats library and build up from there. The excellent Scala with Cats will ease you softly into an FP mindset. It's a bit dated and for scala 2 only but translating to Scala 3 is a very good exercise if you feel so inclined !

Last but not least, Scala is currently the language with one of the best effect systems in my opinion (https://zio.dev/). Kotlin for example has copied the approach with https://arrow-kt.io/ which I think is great actually. But when comparing Scala and Kotlin here, Scala wins by a large margin, it is a completely different world. It's like building a highly concurrent system in Erlang vs C.

Of course, if you don't want to learn things like union types, traits/typeclasses and effects (similar to async/await but more powerful) you will be annoyed by Scala. But once you learned them, you can never go back.

ZIO

Links: - https://dotty.epfl.ch/ - https://scala-native.org/en/stable/ - https://www.scala-js.org/ - https://typelevel.org/ - https://zio.dev/ - https://github.com/scala-native/scala-native/pull/3120 - https://github.com/lampepfl/dotty/pull/16517 - https://dotty.epfl.ch/docs/reference/experimental/index.html - https://scala-cli.virtuslab.org/ - https://scalameta.org/metals/ - https://docs.scala-lang.org/scala3/guides/migration/compatibility-intro.html - https://www.scala-lang.org/blog/2023/04/18/faster-scalajs-development-with-frontend-tooling.html - https://www.scala-lang.org/blog/2022/08/17/long-term-compatibility-plans.html

For the Rx approach, The ZIO framework for Scala has a streaming API that can meet those sorts of requirements. e.g.

This tutorial will introduce how to build from scratch, a REST microservice using the ZIO framework, and examples of ZIO dependency injection, ZIO HTTP, JSON, JDBC, and others from the ZIO environment. The source code is available here

I use ZIO (http://zio.dev) for Scala which makes parallel programming trivial.

Wraps different styles of asynchronicity e.g. callbacks, futures, fibers into one coherent model. And has excellent resource management so you can be sure that when you are forking a task that it will always clean up after itself.

Have yet to see anything that comes close whilst still being practical i.e. you can leverage the very large ecosystem of Java libraries.

The one advantage Rust has over Scala is that it detects data races at compile time, and that's a big time saver if you use low level thread synchronization. However, if you write pure FP code with ZIO or Cats Effect that's basically a non-issue anyway.