Interesting that the Play code optimizations had virtually no effect. Almost identical absolute scores between tests. Clearly something heavy's going on within the Play request handling framework to slow things down, not the code we see.

I was also surprised at the difference between the Java and Scala play test, since I thought they were supposed to be similar. But it looks like the approaches are quite different. The Java DB test uses the ebean ORM while Scala does not. The JSON code also looks a bit different, with the Java version surfacing more Jackson internals. I don't know if these are necessarily "wrong", but perhaps it's not as apples-to-apples a comparison as it could be.