Amazon Software Engineer Internship interview questions

Amazon's SWE internship process this year consisted of two online tests and a final phone interview. I successfully passed the first online test, which consisted of debugging questions and some logic puzzles. The next online test had two typical coding questions (Linked List and LRU Cache). The final phone interview was very basic. I was asked some basic behavioral questions, and then spent most of the time on some technical questions (more Linked List questions). To my disbelief, even though I had solved the problems the interviewer gave me, I received a rejection email in 24 hours. Normally Amazon takes about at least a week to get back to you so I was surprised, especially since I correctly solved the problems. Perhaps something else in my application must have warranted a 24-hour rejection, but it is frustrating, nonetheless.