Postgres and MySQL are very similar, but Mongo has differences in terms of storage type and the CAP theorem. For your requirement, I prefer Postgres (or MySQL) over MongoDB. Mongo gives you no schema which is not always good. on the other hand, it is more common in NodeJS community, so you may find more articles about Node-Mongo stuff. I suggest to stay with RDBMS if possible.
Comparing them end-to-end, Rails comes the most productive in my opinion. But there are bolder parameters you may consider. i.e. no one switches from Django to Rails to improve productivity and vice versa (probably from Laravel to one of those two).
The language's productivity also matters, which both Ruby and Python are better for that.
There is a philosophical difference between #Django and #Rails :
Django supports the "Explicit over Implicit" idea, making it easier for newcomers to understand what's going on. This idea also has downsides. This allows beginners to start working with Django without even learning Django and best practices and defer learning by using references like Stackoverflow.com, which is not a good idea because you potentially don't know things that you don't know! Also, you may find many different project styles.
On the other hand, Rails support the "Convention over configuration" and Scaffolding idea. It's easier for a Rails developer to be added to a new project or just review a random Rails project. Everything has a default and also it has some downsides as well. e.g. As a beginner, everything feels like magic in Rails, and you don't understand what is going on and how Rails understand while you didn't "explicitly" say what do you want sometimes.
Conclusion: Rails and Django are more productive and you can build projects on your own quickly (many giant startups launched this way!).
Node.JS isn't immature, also sometimes shows better performance comparing the mentioned alternatives. But if you suffer from "a million different ways to do everything" and "many decisions to make", Take Ruby on Rails for sure.P.S: for learning RoR I suggest the book/video from Michael Hartl.
It depends on which level and use cases you prefer to work at. Close to the machine? Rust is great but if you need to find more job opportunities, then take C/C++. Java has many job positions but I suggest Kotlin over it. Think about it as a better Java, but fewer job positions. Do you want to do your own projects? So a productive language like Ruby is way better. Like to program front-end apps? Take JS. Find your passion.
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.
