This week we built up the most fundamental layer of the AWS certification: cloud concepts, step by step. We learned what the cloud is (Day 1), where it's laid out (Day 2), how security responsibility is divided (Day 3), and what the standard for good design is (Day 4). Today we fit all these pieces back into one big picture so they settle firmly in your mind.
| Day | Topic | The one line to remember |
|---|---|---|
| 1 | What is cloud computing | Rent resources over the internet and pay for what you use + the six advantages |
| 2 | AWS global infrastructure | Region > Availability Zone > data center, edge locations, global/regional services |
| 3 | Shared Responsibility Model | AWS handles "OF the cloud," the customer handles "IN the cloud" |
| 4 | The six Well-Architected pillars | O-S-R-P-C-S + the value of cloud adoption |
Cloud computing is a model where you rent computing resources over the internet when you need them and pay only for what you use. You rent servers the way you draw electricity from an outlet.
Let's memorize the six advantages AWS emphasizes once more.
💡 Related theory: Underlying the six advantages is "elasticity (automatically growing and shrinking with demand)." In particular, ③ no capacity guessing and ④ speed and agility are possible because of elasticity.
AWS infrastructure has a three-tier structure.
Region ← geographic footholds around the world (Seoul, Tokyo, etc.)
└ Availability Zone (AZ) ← independent facilities within a Region (usually 3 or more)
└ Data center ← the physical buildings that make up an AZ
On top of this come edge locations (caching and delivering content close to users; CloudFront, etc.).
Services fall into two kinds.
💡 Related theory: The basic move in high-availability design is "distribute across two or more AZs." Even if an entire AZ goes down, the service survives in another AZ.
The one core sentence: AWS is responsible for security "OF the cloud"; the customer is responsible for security "IN the cloud."
| AWS responsibility | Customer responsibility |
|---|---|
| Data centers, hardware | Data, data encryption |
| Virtualization (hypervisor) | IAM users and permissions |
| Global network infrastructure | Guest OS patching (EC2), firewall configuration, app security |
And the boundary moves depending on the service. Moving from EC2 → RDS → Lambda (more managed) reduces customer responsibility, but data and IAM permissions are always the customer's job.
💡 Related theory: "The higher the level of abstraction, the narrower the customer's responsibility becomes." But data and permissions never shrink at any level — these two sentences are the master key to Shared Responsibility Model questions.
The six pillars of good cloud design — O-S-R-P-C-S.
When solving questions, first pin down "which pillar is this scenario asking about?" and the answer becomes visible.
This week's four pieces connect into one.
[What] Cloud = rented computing + six advantages (Day 1)
↓
[Where] Global infrastructure spread across Regions, AZs, and edge (Day 2)
↓
[Who's responsible] AWS (OF) vs. customer (IN) — the Shared Responsibility Model (Day 3)
↓
[How to do it well] Good design via the six Well-Architected pillars (Day 4)
That is: know what the cloud is → draw the map of the infrastructure it runs on → understand how responsibility is divided on top of it → and finally acquire the "standard for building it well" — then the foundation of cloud concepts is complete. Starting next week, we place actual AWS services one by one on top of this foundation.
Click a choice to reveal the answer and explanation.
Question 1
Which of the following is the most appropriate definition of the cloud as learned in Week 1?
Question 2
Which of the following correctly describes the structure of AWS global infrastructure?
Question 3
In the Shared Responsibility Model, which area is always the customer's responsibility no matter which service is used?
Question 4
The activity of "protecting the system through least-privilege grants and data encryption" corresponds to which Well-Architected pillar?
Question 5
Which of the following is NOT one of the six advantages of the cloud?