This week started from the fact that network is security''s first defense line. If IAM handles "who can do what," network decides the prior question: "who can even reach where." Can''t reach = can''t attack. Four topics covered this week — VPC design, SG/NACL, Flow Logs, private connectivity — aren''t separate topics. They''re one defense system viewed from four angles.
Today we integrate all four into one scenario for comprehensive review. Complex questions on exams almost always ask multiple layers simultaneously. The sentence "RDS exposed to Internet" contains routing, SG, NACL, and Public IP. Thinking in layered separation is passing criteria.