> expect that rollbacks could have unexpected Expect the unexpected? Sure anything can happen. But paxys is specifically referring to expected (known) side-ef

> expect that rollbacks could have unexpected Expect the unexpected? Sure anything can happen. But paxys is specifically referring to expected (known) side-effects of rollbacks. For example if Foo and Bar are on versions Foo.3 and Bar.3, and we know rolling back to Bar.2 breaks Foo.3, then you broke backwards compatibility. Generally all combinations of possible rollbacks must continue to work, e.g., {Foo.2, Foo.3} x {Bar.2, Bar.3}. The number of rollbacks is limited to 1 or 2 versions, e.g., Foo.1 and Bar.1 cannot be used anymore.