You start with a single VPC, and soon the next questions come up. "I have to communicate with another VPC," "I have to connect to an on-premises DC," "I want private access to S3." Each has a different answer, and the criteria for choosing that answer are a regular SAA exam scenario. If you can clearly map the trade-offs of these four connection methods — Peering, Transit Gateway, VPC Endpoint, and VPN/Direct Connect — half of the network area of the exam is solved.
In this article we look at the when, why, and which trade-offs of each connection method together. Rather than a simple keyword mapping, we take one more pass at "why is this the answer for this scenario."