Outcome
By the end of this lesson, you will be able to read every usage line on a cloud bill and say which of the four things you rent it charges for.
| Prerequisites | L1, I.2, I.3 L1 |
| Time | 9 minutes |
1. Concept
A usage line is one row on the bill. However strange its name, every usage line answers the same three questions:
- What was rented? A machine, some storage, some data movement, a database, or a service that runs on request.
- In what unit? Per hour, per GB-month, per GB moved, or per request (see I.3 L1).
- How much? The amount used, times the unit price, gives the cost on the row.
Clues in the name
Providers name their rows in a compact, technical way. A few clues help:
- Hours, “Hrs” or “running” usually means compute time: a machine that was switched on.
- “GB-Mo”, “GB-month” or “storage” means space kept for a month.
- “Out”, “transfer” or “egress” means data moved, usually charged per GB.
- “Requests”, “API calls” or “invocations” means actions charged per thousand or per million.
- A region code such as
us-east-1oreurope-west1tells you where it happened.
You do not need to know every product name. If the unit is clear, the kind of thing usually is too.
Map each row to one of four things
From I.2, everything you rent is one of four things: compute, storage, network or a database. Put every row in one of those four boxes. Add up each box. Now a 50-line bill is a four-line summary that anyone can read.
2. Worked example
Here is an illustrative month for a small online shop. It is not a real bill, and the prices are round numbers chosen to make the arithmetic easy. The layout and the kinds of rows are realistic.
| # | Service | Usage line | Amount | Unit price | Cost | Kind |
|---|---|---|---|---|---|---|
| 1 | Virtual machines | Machine hours, 4 machines | 2,920 hours | $0.10 per hour | $292.00 | Compute |
| 2 | Virtual machines | Disk storage | 800 GB-month | $0.08 per GB-month | $64.00 | Storage |
| 3 | Virtual machines | Snapshot storage | 400 GB-month | $0.05 per GB-month | $20.00 | Storage |
| 4 | Virtual machines | Public IP addresses, 2 | 1,460 hours | $0.005 per hour | $7.30 | Network |
| 5 | Object storage | Stored files | 2,000 GB-month | $0.02 per GB-month | $40.00 | Storage |
| 6 | Object storage | Read and write requests | 30 million | $0.40 per million | $12.00 | Storage |
| 7 | Managed database | Database machine hours | 730 hours | $0.25 per hour | $182.50 | Database |
| 8 | Managed database | Database storage | 200 GB-month | $0.10 per GB-month | $20.00 | Database |
| 9 | Managed database | Backup storage | 300 GB-month | $0.03 per GB-month | $9.00 | Database |
| 10 | Data transfer | Out to the internet | 1,500 GB | $0.09 per GB | $135.00 | Network |
| 11 | Data transfer | Between two regions | 500 GB | $0.02 per GB | $10.00 | Network |
| 12 | NAT gateway | Gateway hours | 730 hours | $0.05 per hour | $36.50 | Network |
| 13 | NAT gateway | Data processed | 600 GB | $0.05 per GB | $30.00 | Network |
| 14 | Functions | Requests | 5 million | $0.20 per million | $1.00 | Compute |
| 15 | Functions | Compute time | 400,000 GB-seconds | $0.00002 per GB-second | $8.00 | Compute |
| $867.30 |
Fifteen rows. Now the four boxes:
| Kind | Rows | Total |
|---|---|---|
| Compute | 1, 14, 15 | $301.00 |
| Storage | 2, 3, 5, 6 | $136.00 |
| Network | 4, 10, 11, 12, 13 | $218.80 |
| Database | 7, 8, 9 | $211.50 |
| Total | $867.30 |
Three things stand out that the service list alone would hide:
- Network is the second-largest box. It is spread over five rows in three different services, so no single service total shows it. Together those rows are about a quarter of the bill.
- The machines cost more than their hour line. Row 1 is $292, but the disks, snapshots and addresses that come with the machines (rows 2, 3 and 4) add another $91.30.
- Rows 3, 4 and 13 keep billing quietly. Snapshots, reserved addresses and gateway traffic are the kind of rows that outlive the work they were created for (see I.3 L2).
3. Hands-on (5 min: no account needed)
1. Copy the 15-row table above into a spreadsheet.2. For each row, check: amount x unit price = cost.3. Add a column for the four kinds and fill it in without looking at the answer.4. Sum each kind and compare with the four-box table.5. If you have a free-tier account, open last month's bill and try steps 3 and 4 on it.If any row in your own bill will not fit a box, write down its name. It is probably one of the lines covered in the next lesson: credits, tax, support or a third-party charge.
4. Knowledge check
Q1
A row reads “Storage, 500 GB-Mo”. What kind of thing is it, and in what unit?
A. Compute, charged per hour the machine ran
B. Network, charged per GB moved out
C. Storage, charged per GB kept for a month
D. A database, charged per request it served
Show answer
Correct: C. “GB-Mo” means GB-month: space kept for a month. That is storage. Per hour is compute time, and per GB moved is network.
Q2
In the sample bill (illustrative prices), the machine hours row is $292. Why is that not the full cost of running the machines?
A. Because the hours row is always shown before tax is added
B. Their disks, snapshots and addresses bill on separate rows
C. Because the provider rounds every machine row down
D. Because the machines were stopped for half the month
Show answer
Correct: B. One machine produces several rows. The disk, snapshots and addresses that come with it are billed separately, adding $91.30 in this example.
Q3
Network is spread over five rows in three services (illustrative prices). What is the right lesson?
A. Network rows spread across services can add up to a large share
B. Network rows are always errors and should be disputed
C. Network costs can be safely ignored because each row is small
D. Network rows only appear on Google Cloud bills
Show answer
Correct: A. Adding rows into the four boxes shows what the row-by-row view hides. Here, network is about a quarter of the bill. B, C and D are wrong: these are normal charges and appear on every provider’s bill.
5. Apply
Take any cloud bill you have access to and build the four-box summary: compute, storage, network, database. Share that summary, not the 50-line bill, with someone who is not technical. Then point to the largest box and ask the people who run the systems why it is that size.
Related lessons
- L1, Where the bill lives and how it is laid out
- L3, Credits, tax and support, and what comes next (next)
- I.2 L5: One app, four meters
Glossary terms touched
Egress · NAT Gateway · API request charge