I'm coming from Rails (7 years) and am now looking at Spring Boot - I've also experimented with Scala and Play, Scalatra, Sinatra, Go, .Net MVC, Elixir/Phoenix.

I'm coming from Rails (7 years) and am now looking at Spring Boot - I've also experimented with Scala and Play, Scalatra, Sinatra, Go, .Net MVC, Elixir/Phoenix. I'm impressed with what I've seen so far from Spring boot. I've only got a experimental app connecting to a database and producing JSON, but no XML config yet other than my POM. I'm actually very impressed with how much code I'm not writing, which is something I've become accustomed to with Rails and was a surprise from Spring/Java. On your point about maintainability: If you're writing a large app that you're likely to be supporting for the next 10 years, I like the idea that backwards compatibility or at least some form of lenient deprecation is in there. Once you're over 25k LOC do you really want breaking changes every framework update which require you to drop all your planned features and improvements and change all your code again?