Amazon Area Manager interview questions

I reached out to a Recruiter through Linkedin back in January about an Area Manager position with Amazon. He responded to me quickly and told me someone would be in touch with me within the next week for a phone screening. A week later a Recruiter called me and we had a brief phone conversation. He said he would like to call me in a month to discuss opportunities. A month later we spoke again for about 5 minutes and he told me he would like to speak with me a month later. After about 3 or 4 phone calls I finally had a 30 minute phone interview with a Senior Operations Manager at the Hazleton, PA location in March. He told me he wanted to have me fly down to Hazleton for an interview. It took about another month for me to get a face to face interview. This is the most stressful interview process I have ever been through. Before you even travel for the interview they e-mail you 4 case studies to do and then you have to e-mail them to the Recruiter. When you go to the location they have you work on a throughput math problem (you should probably study up on it). After that you go on a tour of the Distribution Center and then have a panel interview with 3 managers and yourself. Talk about a grilling!! You have to go over your answer on a whiteboard. On top of that they come up with another alternative you have to figure out. After that you have to explain a couple of your case study answers. This was my least favorite part of the process. Afer that I met with an HR Manager and another GM and had a 2 on 1 interview with them which lasted about 30 minutes. This concluded the interview process which took 3 hours total. I honestly felt stupid when I left the interview which is not a good feeling to have. I have been on a lot of interviews in my life and this was by far the most difficult. They do a lot of recruiting out of the military so a lot of the guys who work here tend to be pretty serious. It was an interesting interview process but I don't expect an offer to come out of it since I feel I did a poor job during the interview process.