The benchmark suited used the STDLIB json parser which is slow as hell. How slow is it? In 2011 there was a proposal to deprecate it, which never happened [1].

Why? STDLIB parser loads the file line-by-line, then copies line by line into a new buffer that joins the strings together. Then the parser is called. The Scala community normally circumvents by using non-standard community developed solutions.

Furthermore JIT vs Compiled language benchmarks are pretty unfair to JIT'd languages. Especially for the JVM which doesn't start to compile sections until >10,000 calls.

[1] https://groups.google.com/forum/m/#!msg/scala-user/P7-8PEUUj...