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Starts this lesson and continues through 7 more to the end of certification prep.
Open the Domain 4 page of the exam guide (fetched 2026-09-25) and look at the first two "Knowledge of" bullets under every one of the four task statements. They are identical:
"AWS cost management service features (for example, cost allocation tags, multi-account billing)" "AWS cost management tools with appropriate use cases (for example, AWS Cost Explorer, AWS Budgets, AWS Cost and Usage Report)"
Four task statements, the same two bullets, four times. That's AWS telling you the tools are not a storage topic or a compute topic. They sit under all of them. So this lesson covers them once, and the other four lessons assume them.
Task 4.4 also has a skill that is really about these tools: "Reviewing existing workloads for network optimizations". You cannot review what you cannot see.
The distinguishing question is: what does the stem want to do with the money?
understand where it went, spot a trend → Cost Explorer
be warned (or stopped) before it goes → AWS Budgets (+ budget actions)
the raw line items, into your own tools → Cost and Usage Report / Data Exports
split one bill by team, app, cost centre → cost allocation tags
one bill, pooled discounts, many accounts → Organizations consolidated billing
tell me what to resize or delete → Compute Optimizer (+ Trusted Advisor)
From Analyzing your costs and usage with AWS Cost Explorer, fetched 2026-09-25:
"AWS Cost Explorer is a tool that enables you to view and analyze your costs and usage. … You can view data for up to the last 13 months, forecast how much you're likely to spend for the next 18 months, and get recommendations for what Reserved Instances to purchase."
| Fact | Value, verbatim where quoted |
|---|---|
| History | "up to the last 13 months" |
| Forecast | "the next 18 months" |
| Refresh | "at least once every 24 hours" |
| First-time setup | current month "available for viewing in about 24 hours"; the rest "a few days longer" |
| Console | "free of charge" |
| API | "Each paginated API request incurs a charge of $0.01" |
| Can you turn it off? | "You can't disable Cost Explorer after you enable it." |
| Dataset | "the same dataset that is used to generate the AWS Cost and Usage Reports" |
⚠️ The API charge is the trap in the lab, not on the exam. A script that pages through
get-cost-and-usage in a loop is billed per request. The console is free.
Cost Explorer is also where Savings Plans recommendations live — the Savings Plans guide says to "use AWS Cost Explorer to view your recommended Savings Plans commitment" (lesson 3).
From Managing your costs with AWS Budgets, fetched 2026-09-25. Six budget types, verbatim names:
| Budget type | What it alerts on |
|---|---|
| Cost | "costs approach or exceed your defined threshold" |
| Usage | "usage approaches or exceeds your set threshold" |
| RI utilization | RI usage "falls below this level" → unused RIs |
| RI coverage | "percentage of your instance hours covered by RIs falls below this level" |
| Savings Plans utilization | SP usage "drops below this level" |
| Savings Plans coverage | "percentage of your eligible usage covered by Savings Plans falls below this level" |
Two details the exam uses:
And the freshness caveat, verbatim — it matters for "why didn't the alert stop the overspend?":
"AWS Budgets information is updated up to three times a day. Updates typically occur 8–12 hours after the previous update."
"There can be a delay between when you incur a charge and when you receive a notification … You might incur additional costs or usage that exceed your budget notification threshold before AWS Budgets can notify you."
⚠️ A budget is a smoke alarm, not a circuit breaker. It can fire late, and on its own it stops nothing.
From Configuring budget actions, fetched 2026-09-25:
"You can use AWS Budgets to run an action on your behalf when a budget exceeds a certain cost or usage threshold. … configure a budget action to run either automatically or after your manual approval."
"Your available actions include applying an IAM policy or a service control policy (SCP). They also include targeting specific Amazon EC2 or Amazon RDS instances in your account."
⚠️ Cross-account limit, verbatim: "From the management account, you can apply an SCP to another account. However, you can't target Amazon EC2 or Amazon RDS instances in another account."
So "stop developers provisioning anything once the sandbox hits its budget" → budget action applying a deny SCP or IAM policy. "Stop the instances in this account" → budget action targeting EC2/RDS.
From What are AWS Cost and Usage Reports?, fetched 2026-09-25:
"AWS Cost and Usage Reports (AWS CUR) contains the most comprehensive set of cost and usage data available. You can use Cost and Usage Reports to publish your AWS billing reports to an Amazon Simple Storage Service (Amazon S3) bucket that you own. You can receive reports that break down your costs by the hour, day, or month, by product or product resource, or by tags that you define yourself."
From What is AWS Data Exports?, fetched 2026-09-25, the current home for this data is Data Exports, with export types including:
⚠️ The exam guide still says "AWS Cost and Usage Report". The HTML guide wording is unchanged (fetched 2026-09-25). On the exam, "Cost and Usage Report" is the answer to "most granular / most comprehensive / hourly / by resource / load into Athena". In the console you will find it under Data Exports as CUR 2.0.
| Cost Explorer | CUR / Data Exports | |
|---|---|---|
| Shape | interactive graphs, filters, forecast | files in your S3 bucket |
| Depth | 13 months back | the full line-item detail, per hour/resource |
| Who uses it | a person looking | a pipeline querying (Athena, Redshift, Quick) |
| Answer to | "which service grew last quarter?" | "charge back every resource-hour to its team" |
The skill "Reviewing existing workloads for network optimizations" is a CUR job. From
Understanding data transfer charges,
fetched 2026-09-25, the lineItem/UsageType column tells you which kind of transfer you're paying for:
| Usage type pattern | What it is |
|---|---|
<Region>-DataTransfer-Regional-Bytes |
between AZs in one Region |
<Src>-<Dst>-AWS-Out-Bytes |
out of one Region into another (this line carries the charge) |
<Region>-DataTransfer-Out-Bytes |
to the internet |
ends DataXfer-Out / DataXfer-Out:dc.3 |
Direct Connect (public / private-or-transit VIF) |
Lesson 5 is built on those rows.
From Organizing and tracking costs using AWS cost allocation tags, fetched 2026-09-25:
"AWS provides two types of cost allocation tags, an AWS-generated tags and user-defined tags. … You must activate both types of tags separately before they can appear in Cost Explorer or on a cost allocation report."
The details that decide questions:
user prefix, and the AWS-generated tag uses the aws:
prefix." AWS's example of a generated tag is createdBy.⚠️ Tagging a resource is not enough. The tag has to be activated for cost allocation, by the management account, and it takes up to a day to appear. "We tagged everything last week and Cost Explorer shows nothing grouped by tag" → nobody activated them.
⚠️ The page lists a "Backfill cost allocation tags" topic but I did not fetch it. Do not assume tags
apply retroactively or that they don't — read
docs.aws.amazon.com/awsaccountbilling/latest/aboutv2/cost-allocation-backfill.html.
From Consolidating billing for AWS Organizations, fetched 2026-09-25:
"Every organization in AWS Organizations has a management account that pays the charges of all the member accounts."
The four benefits, verbatim headings:
⚠️ The discount-sharing line is the examinable one. A Reserved Instance or Savings Plan bought in one account can reduce the bill for matching usage in another account in the same organization. The RDS reserved-instance guide says the same for databases: "all accounts in the organization can receive the hourly cost benefit of reserved DB instances that are purchased by any other account" (lesson 4).
And a quirk worth one sentence in an interview: "When a member account leaves an organization, the member account can no longer access Cost Explorer data that was generated when the account was in the organization."
From What is AWS Compute Optimizer?, fetched 2026-09-25:
"AWS Compute Optimizer is a service that analyzes your AWS resources' configuration and utilization metrics to provide you with rightsizing recommendations and identify idle resources."
| Fact | Verbatim |
|---|---|
| Opt-in | "You must opt in to have Compute Optimizer analyze your AWS resources." |
| Default lookback | CloudWatch metrics "for the last 14 days" |
| Extended lookback | "enhanced infrastructure metrics (paid feature)… extends the metrics analysis lookback period … to 93 days" |
| Org-wide | findings "across multiple accounts, if you opt in the management account of an organization" |
Supported resources (from the page): EC2 instances · EC2 Auto Scaling groups · EBS volumes · Lambda functions · ECS services on Fargate · commercial software licenses · Aurora and RDS databases · NAT Gateway · DynamoDB · ElastiCache · MemoryDB · DocumentDB · WorkSpaces · SageMaker.
⚠️ Memory is the blind spot. The page lists the EC2 metrics it analyzes as "CPU utilization,
network in and out, disk read and write", and separately notes it "can ingest and analyze external EC2
memory utilization metrics from observability products like Datadog and Dynatrace". I did not fetch
the metrics page, so I make no claim about whether CloudWatch-agent memory metrics are used — read
docs.aws.amazon.com/compute-optimizer/latest/ug/metrics.html before relying on it.
From Cost optimization checks, fetched 2026-09-25. Check names that appear on the page include:
⚠️ Which support plans unlock which cost checks is not on the page I fetched in a form I can quote.
Do not answer a "which Support plan gives full Trusted Advisor" question from this lesson — read
docs.aws.amazon.com/awssupport/latest/user/trusted-advisor.html. I also don't quote each check's
thresholds here; read the check definitions on the page.
Discriminator: Compute Optimizer vs Trusted Advisor. Compute Optimizer is resize this to that from 14 (or 93) days of metrics. Trusted Advisor is a checklist across many categories, of which cost is one, and it catches waste that isn't a sizing problem — an unattached Elastic IP, an idle load balancer.
| The stem says | Answer |
|---|---|
| "visualise spend by service over the last year and forecast next quarter" | Cost Explorer |
| "alert finance when forecasted monthly spend exceeds $X" | AWS Budgets, forecasted threshold |
| "automatically prevent new resources once the sandbox exceeds its budget" | Budget action → deny SCP / IAM policy |
| "most granular, hourly, per-resource data, queried with Athena" | Cost and Usage Report (CUR 2.0 via Data Exports) |
| "charge back costs to each department" | cost allocation tags, activated in the management account |
| "tags applied but not showing in Cost Explorer" | tags not activated (or < 24 h) |
| "share Reserved Instance discounts across 12 accounts" | Organizations consolidated billing |
| "recommend smaller instance types from utilisation" | Compute Optimizer |
| "find unattached Elastic IPs and idle load balancers" | Trusted Advisor cost checks |
| "alert when RIs are going unused" | RI utilization budget |
DataTransfer-Regional-Bytes line. That one screen sets up lesson 5.