Phone interview was an easy. Is the on-site also going to be easy or medium/hard?
Medium
Probably medium but on the lower end of medium because they care about leadership principles and not if you can code.
It's not SWE at Amazon. It's SDE.
Medium-Hard
Difficultly depends on the interviewers and the role they are trying to fill. There is no standard difficultly level AFAICT
Easy/medium. Totally depends on the interviewer though