Too Long; Didn't Read
VPC is the topic that flies under the radar of many Software Developers, despite being present in every AWS account. Big companies have Ops/DevOps/SysAdmin/SRE/Security departments that take care of VPC settings. Startups often don't bother tuning it - everything works with default settings after all. VPC operates on the regional level, meaning that if you want your application to span multiple regions you will need to perform VPC setup for each region separately and configure a VPC peering between them.