In Drools 7 a big amount of time is spent to manage a NoSuchFieldExceptions in Class.getDeclaredField. This happens when client code tries to get/set a value of a non-existent field of a Fact Type: while in Drools 6 it immediately returns a null, in Drools 7 causes the execution of a recursive routine introspecting the class itself. Very likely this change behaviour has been introduced by this commit https://github.com/kiegroup/drools/commit/435f7ead86e20b361e25abd60f1b228b5816ede1