tapir VS Akka

You're not confined to the usual suggestions below (play, http4s). There's a ton of options. (I wrote test cases using a bunch of different frameworks a few years ago at https://github.com/hohonuuli/msdemos). Having written services using a variety of frameworks in production, I would strongly suggest using one that auto-generates API docs (openapi, swagger) for you. That will save you a huge amount of time later on. For heavier services, like the one at https://fathomnet.org/, I tend to the Java side (Quarkus is my current top choice, but Micronaut and Helidon are both great). For everything else I use Scala. My go-to right now is tapir using a vertx backend. See https://tapir.softwaremill.com/

Tapir is a Scala framework. (which runs on the JDK) Since the recent release of version 1.0, it's become my go to for many projects. It doens't provide much in the way of integrations with 3rd party frameworks, but I actually prefer that. It does autogenerate great swagger docs though.

I do wonder where the recommendation to use http4s for beginners came from. http4s is a very capable library (and if you care much about composition it is excellent), but I wouldn't describe the documentation as beginner friendly.

A slightly better starting point for scala 3 + type-safe server building is tapir e.g. https://github.com/softwaremill/tapir/blob/master/examples3/... . With that, you get a declarative definition of your endpoints (+ error types, auth, etc.) that you can use for both servers and clients, which comes very handy when writing integration tests of course.

> absolutely ridiculous the fetishization of extremely complex FP and type-level hacking that goes on in the ecosystem

An alternative way to look at it is that there is a lot of essential domain complexity that gets encoded via the type system to let the compiler do the hard work. That "extremely complex FP" does not arrive out of nowhere - I really recommend at least skimming through the slides from rossabaker, the http4s designer, that motivate where the core type signature comes from https://rossabaker.github.io/boston-http4s/#2

I suppose one of the "features" that I like about the (typelevel) community is that the approach of "worse is better" is not taken, and a lot of effort is expended to make things correct, modular and orthogonal. This has the drawback of increased upfront complexity, that anecdotally pays off the moment your compiler does not error and the program runs as intended.

Did you try tapir? There is a module for deploying aws lambda with Scala js. Not sure whether it is compatible with Scala 3, I am sticking with Scala 2 until Scala 3 gets more mature.

I'm aware, but it's a design decision that was made on purpose, and which I find in practice not a big problem at all.

Backend is source of truth for types on frontend (backend generated OpenAPI definition with tapir, frontend takes it with orval)

In all cases I would strongly suggest to have a look at Tapir, regardless of the server implementation that you pick.

Check the infographic below, to see this tool history, functionalities and more. Make sure, to take tAPIr for a spin here and share your feedback with us in the comment section!

Tapir is awesome, and you can pick the server backend according to your preferred ecosystem (for instance http4s + doobie, Zio + Quill, Akka + Slick, ...)

Finally I would strongly recommend having a look at Tapir. Even if you don't need to share endpoints or generate OpenAPI documentation, it provides a really neat abstraction on top of http4s.

Kotlin also has a construct for asynchronous collections/streams. Kotlin's version of AsyncSequence is called a Flow. Just as Swift's AsyncSequence builds upon prior experience with RxSwift and Combine, Kotlin's Flow APIs build upon earlier stream/collection APIs in the JVM ecosystem: Java's RxJava, Java8 Streams, Project Reactor, and Scala's Akka.

First-class distributed and multicore computing. Swift has first-class “actors” and “distributed” methods. Unison, Erlang, and Elixir are built with distributed being one of the #1 concerns. Though first-class is not super common and I don't really expect it to be because usually libraries are enough (e.g. Scala has Akka and is used WIDELY for distributed); whereas something like linear types and typed effects, you can't emulate in a library.

Akka is a library that implements the actor model for JVM languages. Mainly in Scala, but you can use it in Java too, and maybe others. It doesn't feel as ergonomic as Elixir, but if Elixir is too "out there" for the decision makers in your case, this might be a friendlier alternative.

Kalix builds on the lessons we have learned from more than a decade of building Akka (leveraging the actor model) and our experience helping large (and small) enterprises move to the cloud and use it in the most time, cost, and resource-efficient way possible.

Note Akka, the Java & friends framework, is working with the actor model and have as main inspiration Erlang to mimic some features of the BEAM on top of the JVM.

Looking back at real dates, I started learning the language (Scala) back in 2008 because it was something new and trendy that interested me. I started spending some serious time with it in 2009 (helping out other newcomers and making small contributions to various projects), and then in 2010 became a core contributor to the Akka project (you can find me a little ways down this list: https://github.com/akka/akka/graphs/contributors). For the most part I worked on the features I wanted to, but worked on other things if a user asked nicely. Akka became very popular in the early 2010s, so all of a sudden I had highly sought after skills. Got hired by a London based company and moved myself and my family from Canada over here. But even today, that exposure I got 10 years ago still helps me to land new contracts.

In the open source world, Akka, the most popular actor system library in the JVM ecosystem, that’s heavily used in tonnes of open source projects, recently went from “free and open source” to “paid/proprietary and source available.” https://github.com/akka/akka/pull/31561

Same strategy - the pricing is insanely high (for a library), and the project is effectively dead now, but it’ll take some larger enterprises awhile to move away from.

Lightbend, the company owning Akka, recently shared a blog post signed by the CEO announcing a license change from Apache 2.0 to Business Source License 1.1, a proprietary license. You can already find it in this PR, merged a couple days ago.

Akka 2.6 is on the open source Apache license, that is unchanged (its not possible for Lightbend to change an existing license). Its only the new Akka 2.7 which has the BSL license, so as long as you don't upgrade you are fine. See https://github.com/akka/akka/pull/31561.