Linux system

 Here is the link.

Systems

More specifically, linux troubleshooting and debugging. Understanding things like memory, io, cpu, shell, memory etc. would be pretty helpful. Knowing how to actually write a unix shell would also be a good idea. What tools might you use to debug something? On another note, this interview will likely push your boundaries of what you know (and how to implement it).

Design/Architecture 

Interview is all about taking an ambiguous question of how you might build a system and letting you guide the way. Your interviewer will add in constraints when necessary and the idea is to get a simple, workable solution on the board. Things like load and monitoring are things you might consider. What you consider is just as important as to what you don’t. So ask clarifying questions and gather requirements when appropriate.