This is advice regardless of your background and requirements. The Play framework has a terrible and complicated design, don't risk it. I even suggest Spring and Kotlin over it! You can use Scala for small services and Data Engineering stuff and benefit optimizations and threading of JVM. RoR, on the other hand, has a huge development speed, which I believe is a big advantage cause you can handle performance bottlenecks later. Also, Scala has another downside, which is featureful in terms of OO and FP paradigms, which makes anyone write code freely with any personal style and makes it a problem in a team, Hence a coding style has to be defined if there would be Scala development team.