The physical cloud
The cloud is very physical: AWS runs dozens of Regions (independent geographic areas — us-east-1 N. Virginia, eu-west-1 Ireland, af-south-1 Cape Town). Each Region contains multiple Availability Zones (AZs) — physically separate data-center clusters, kilometers apart, with independent power and networking, connected by fast private fiber.
Why it matters, permanently:
- A Region is a choice: latency to your users, data-residency law, price (Regions differ), and service availability. This course uses one Region consistently — pick it Week 1, stay in it (resources in other Regions are invisible in the console's default view, which is how students "lose" instances that keep billing).
- An AZ failing is normal; designing for it is your job. Everything important in this course runs in at least two AZs — the habit starts in Week 5 and is graded through the capstone.
- Edge locations — hundreds of small sites worldwide where CloudFront (Week 7) caches your content close to users. More edge locations than AZs, more AZs than Regions.
The shared responsibility model (exam favorite, real-life essential)
AWS secures the cloud; you secure what's IN the cloud.
- AWS's side: physical data centers, hardware, the hypervisor, the managed services' underlying infrastructure. You never audit their server rooms; that's the deal.
- Your side: your data, IAM users and permissions, security group rules, OS patching on EC2, encryption choices, what you leave publicly readable.
The line moves with the service model: on EC2 (IaaS) you patch the OS; on RDS (PaaS-ish) AWS patches the engine but you manage users and network access; on Lambda you own basically just code and permissions.
Practical translation: every breach headline that says "S3 bucket exposed millions of records" was a customer-side failure — a misconfigured bucket policy, not a hacked data center. The whole point of Weeks 2, 4, and 10 is making sure that's never you.
Diagram habit starts now
This week's project includes a one-page diagram of Regions → AZs → edge locations in your own hand. Every week of this course starts with a diagram — architects draw before they build, and by Week 12 that reflex is graded.