Your question is Algorithms, Big-O, and Distributed Issues. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
What is the big-O complexity of searching an array, and how could you improve it? Also explain the complexity of a Hashtable lookup in Java, including worst-case behavior, and what issues arise in distributed systems.