Amazon Software Development Engineer interview questions

First there was online programming test. It was required to write 2 functions which both fulfilled different purpose. Both functions had lots of unit tests where all has to pass. Then there was small brief about my coding behaviour (why I did it as I did it). And at the end some HR style questionnaire. This was easy part. After few weeks there was face to face interview with 4 different people 1 hour each, 10 minutes break. Lots of questions like tell me about time when you failed, etc. plus coding on white board. This was difficult especially last hour because I was exhausted. (advice bring some sugar or energy drink with yourself).