Oracle Developer interview questions

I applied through college and recieved a reply that I matched with a couple of teams. One of the teams was the Cloud and Silicon Team. I had one phone interview with two interviewers on the other side (one PM and one engineer). They asked me details about my projects and discussed multithreading/concurrency problems. The second interviewer was based in Texas. He called me up and jumped on directly to a system design question where I had to design a banking transaction system that has services in New York, Tokyo and Bangalore. Each of them has a database at the location that only the server at the same location can access. Somehow, all the data in the three databases in always replicated. He wanted me to build a system somehow that would solve concurrency issues when a request from one user was recieved at all three servers at the same time. Now, he placed a few constraints. 1. The servers cannot forward requests to each other. 2. They cannot access (or lock) each other's databases. 3. We cannot add more servers. 4. We are not allowed any global timestamp. Basically, he added constraints as I gave the solution. When I had no answer left, he blurted something like "Nowadays, graduates have no idea about building systems". Then he moved on and said "Do you have any questions?". I responded "Sir, could you tell me the answer to the same question?". Obviously, the guy had no answer. I'm glad I am not a part of his team.