-rw-r--r-- 1 razzle razzle 2.8M May  6 09:25 sparkTest-0.1.jar
-rw-r--r-- 1 razzle razzle 4.0M May  6 09:09 rapidoidTest-0.1.jar

Created "Hello world" fatJars for spark and rapidoid, this is the result. There's one called Pippo also which claims to be smaller. I'll try that one out later.