I was contacted by someone in engineering management, had a 30 min call and they were knowing about my experience and we talked and the interview went well. After that there was an interview with an engineer , he asked me to design an optimized robot delivery system for a warehouse, etc. I know the basics of the optimization problem, resource constraints, timing issues, etc and I explained it well. However, obviously, he didn't like something in my personality as there were no follow-up emails, no replies, and complete ghosting