Outcome
By the end of this lesson, you will be able to list every meter a simple web app runs and add them up into a monthly estimate.
| Prerequisites | L1 to L4 |
| Time | 6 minutes |
1. Concept
One app is never one charge. Even the simplest website rents something from all four groups at once.
| What you rent | What it is | What the meter counts |
|---|---|---|
| Compute | Machines that run the app | Hours switched on, by size |
| Storage | Disks, files and snapshots | GB kept per month |
| Network | Data moving out, plus traffic equipment | GB moved out, and hours for items like load balancers |
| Database | Organised records, run for you | Hours and GB, or requests and GB |
When someone asks “what does our website cost?”, the honest answer is the sum across all four. Quoting only the machines, which is the line people notice first, usually gives a number that is too low.
2. Worked example
A small online shop. All prices are illustrative and round.
| Group | Item | Monthly cost |
|---|---|---|
| Compute | Two web VMs, on all month | $146 |
| Storage | Two 100 GB disks | $20 |
| Storage | Product images in object storage | $5 |
| Storage | Nightly snapshots, kept 30 days | $15 |
| Network | Customer downloads (egress) | $45 |
| Network | Load balancer | $18 |
| Database | Managed database with a standby copy | $300 |
| Total | $549 |
The two VMs are what the team pictures when they think of “the website”. They are $146 of a $549 bill, about a quarter. The database, which nobody looks at, is more than half.
3. Hands-on (4 min: no account needed)
1. Pick an app you use every day: a shopping site, a booking app or a news site.2. Write down one thing it would need from each group: compute (what runs it), storage (what it keeps), network (what it sends you), database (what it looks up).3. For each one, write the meter it would run on: hours, GB kept, GB moved, or requests.There is no single right answer. The aim is to see that every app you use is renting from all four groups at once.
4. Knowledge check
Q1
Someone says “our website costs $146 a month” (illustrative prices) because that is the VM line. What is most likely true?
A. That is the full cost, since the website runs on those VMs
B. The true cost is lower, because VMs include storage and network
C. The true cost is higher, as storage, network and database charge too
D. The cost cannot be estimated without a full engineering review
Show answer
Correct: C. An app rents from all four groups, so the compute line is only part of the cost. VMs do not include their disks or data transfer, and the total can be added up from the bill without a long review.
Q2
Which meter does customer download traffic run on?
A. GB moved out of the cloud
B. Hours a machine is switched on
C. GB kept per month
D. Number of database tables
Show answer
Correct: A. Downloads are outbound data, or egress, charged per GB moved. Hours belong to compute and GB kept to storage.
Q3
In the worked example, which group cost the most?
A. Compute
B. Storage
C. Network
D. Database
Show answer
Correct: D. The managed database with a standby copy was $300 of $549. It is a common pattern: the part nobody pictures is often the biggest.
5. Apply
Before agreeing with any “this costs X” figure, run the four-group check. Compute, storage, network, database: is each one in the number? If one is missing, the figure is too low. This simple habit is what Cloud Cost Foundations builds on.