It a pretty fair assumption to expect the Java runtime itself to be in an OS-level sandbox, Google would never treat that much native code as the last layer of

It a pretty fair assumption to expect the Java runtime itself to be in an OS-level sandbox, Google would never treat that much native code as the last layer of security. The App Engine CPython runtime can also be subverted in a variety of ways, but about the most exciting thing you can trigger here is for the process hosting your code to immediately be killed.