Opening Scenario
You've deployed a new service to AWS. It runs fine in isolation, but it can't connect to the database in another subnet. Your API gateway can't reach the service. The service can't reach the internet to fetch a configuration file. No error messages beyond "connection refused" and "connection timed out." Everything looks correct in your application code.
The problem isn't your code. It's the network configuration around it. Cloud networking has its own concepts — VPCs, subnets, security groups, route tables — and until they click, every deployment feels like guessing.
Question Progression
1. What is a VPC and why does your service live inside one?
Question: When you launch an EC2 instance or a container in AWS, it doesn't connect directly to the public internet. Why? What is it actually connected to?
Reasoning: On bare metal, every server has a NIC connected to a physical network. In the cloud,…
In the full tutorial
- When to Reach for This