Google App Engine Flexible-Deploy WAR or JAR application?

Question

I see in a lot of sample projects for GAE Flexible starting to embrace the notion of a "fat" JAR (using an embedded web server like Jetty, Springboot, SparkJava or Tomcat) vs. the traditional WAR deploy. Both methods involve a single JVM process (ie no matter how many WARs are deployed to Tomcat, it's all the same JVM process).

Under what circumstances is either deployment method preferable over the other in Google App Engine Flexible?

Answer 1

GAE has 2 types of environments for Java, one is docker-based (new) and another is what they called 'scalable'. For first type, there is almost no limits for frameworks or libraries, for second - very restrictive set of supported libs. Second type of environment requires WAR package, first one does not have any requirements for packaging, simply because this is docker image.

Check this for more: https://cloud.google.com/appengine/docs/java/