msdemos VS Play

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/

I've put together simple examples (in Scala 3), that all do exactly the same thing, using various frameworks and benchmarked them. The source code is at https://github.com/hohonuuli/msdemos. For the record, I usually use Scalatra for Scala projects, Helidon or Micronaut for Java projects. If you're new and looking for something super simple, try out Cask or SparkJava.

I've written sample apps in Scala 3 that all do the same thing at https://github.com/hohonuuli/msdemos using akka-http (some issues at the moment), cask, finatra (which doesn't work with Scala 3), helidon, http4s, javalin, scalatra, sparkjava, vertx, and zio-http. I wrote those as an exercise in understanding particular frameworks and benchmarking them. (I write a lot of microservices). You can peruse the code there to get a feel for what it takes to write a service in a particular framework

My major complain here is that, as far as being a web framework there is precious little information here about the framework. How does this framework scale with multiple requests? What concurrency strategy is it using (threads, processes, actors, etc?). Is this opinionated (it doesn't seem so but it also doesn't say it isn't either). How does this work with popular libraries x,y,z. The full docs have a little bit more information, but not a ton. But mostly there are some cute toy examples and "built in python" and thats about it.

Lets compare this with for example play https://www.playframework.com/ I know from this that it built on Akka, its stateless, aims for predictable resource consumption, has non-blocking io, etc. There is a ton of really important information on what does this web framework actually do that is really important when you are making a choice of a framework.

I have no idea how good this framework is, but besides a few toy examples, I can't see anything that makes me thing "wow this is great I need to use this".

A web application framework for Java/Scala: https://www.playframework.com/

Scala 3 migration isn't as simple as migrating other apps, you can track the work at https://github.com/playframework/playframework/issues/11260

And there are frameworks you can use to make development easier, like Play. And Java has plenty of choices for dependency injection frameworks.

However do note, Play should be perfectly usable as well, and it's still maintained by the community: https://github.com/playframework/playframework/issues/11649

In university I learned a bit of Java, so maybe I could use it professionally I guess?. There were many options to choose from. DropWizard, Spark, Play Framework. But the more documented one in the internet I found was Springboot, besides there were some courses in spanish and some friends that knew something about Springboot, so I give it a chance.

For a backend web server I use Play - https://www.playframework.com/ which I find to be the easiest one as a backend web server. For learning/using spark I found this course from coursera to be very useful. https://www.coursera.org/learn/scala-spark-big-data