Tagging, cost categories and chargeback: SAP-C03 study notes and practice questions
What to know about Tagging, cost categories and chargeback for the SAP-C03 exam, from the Cost-Optimized Architecture Design domain (15% of the exam guide), then 1 free question to test it. Part of the SAP-C03 study guide.
These questions describe a company that can’t tell which team, product or customer drives its AWS bill, and ask for a design that allocates cost accurately with little manual work.
Tagging strategy
Agree a small set of mandatory keys (such as CostCenter, Application, Environment, Owner) with allowed values, and keep the values low-cardinality.
Account structure is the strongest allocation boundary. Separate accounts per workload or business unit, grouped in OUs, allocate cost without depending on tags at all.
User-defined tags must be activated as cost allocation tags in the management (payer) account before they appear in Cost Explorer and the CUR. Activation is not retroactive, and new tags can take up to 24 hours to show up. AWS-generated tags such as aws:createdBy can be activated too.
Tag through IaC (CloudFormation stack tags or CDK Tags.of() propagate to resources) so tags are present at creation.
Enforcing tags
Control
What it does
Tag policies (Organizations)
Standardize key case and allowed values; with enforcement on, block noncompliant tagging operations on chosen resource types; report compliance across accounts
SCP with a Null condition on aws:RequestTag/<key>
Denies create calls that omit a required tag (preventive)
AWS Config required-tags rule
Detects resources missing tags; remediate with Systems Manager Automation (detective)
CloudFormation Hooks or Control Tower proactive controls
Block noncompliant templates before deployment
Tag policies alone don’t stop a resource being created without a tag; pair them with an SCP or proactive control when “untagged resources must never be created”.
Splitting shared costs
AWS Cost Categories map accounts, tags, services and other categories into business-level groups (such as “Retail” or “Platform”). Categories show up as a dimension in Cost Explorer, Budgets, Cost Anomaly Detection and the CUR.
Split charge rules in cost categories spread shared costs (a shared network account, support fees) across groups proportionally, evenly or by fixed percentages.
Split cost allocation data for Amazon ECS and Amazon EKS divides the cost of shared EC2 instances to individual tasks or pods by their CPU and memory reservation or use, so container tenants can be charged back from the CUR.
AWS Billing Conductor produces pro forma bills with custom rates for showback to business units or resale customers.
Generative AI spend
IAM principal attribution puts Bedrock spend in Cost Explorer and CUR 2.0 by calling identity and its principal or session tags (team, cost center). An LLM gateway can assume a role per tenant with session tags to keep per-tenant cost.
Application inference profiles carry cost allocation tags per application or tenant.
Per-request metadata plus model invocation logging gives per-prompt token detail for deeper analysis.
CloudWatch Bedrock metrics show token counts by model in near real time. See AI costs.
How to choose
Scenario wording
Pick
“Block creation of resources without a CostCenter tag”
SCP with aws:RequestTag and Null condition
“Standardize tag spelling across the organization”
Tag policies
“Allocate shared networking costs to business units”
Cost categories with split charge rules
“Charge back tenants on a shared EKS cluster”
Split cost allocation data for EKS
“Bedrock cost per application”
Tagged application inference profiles
Common traps
Forgetting to activate tags, or expecting history to be retagged.
Tag policies alone as a way to block untagged resources.
High-cardinality values such as request IDs as cost allocation tags.
Allocating container costs by instance tags when many teams share a node.
A retailer runs 40 AWS accounts in one organization. Its commerce, marketing and logistics business units each need a monthly charge-back, and the platform team runs one shared Amazon EKS cluster in a single account for all three units.
The shared cluster's cost must be split by the namespaces each unit runs in, and the charge-back must cover accounts that are owned by one unit only. The finance team wants the split to appear in the normal billing data, with no spreadsheets.
Which solution meets these requirements?
Choose one answer.
AA. Create an AWS Budgets budget for each business unit's expected spend, and have each unit's manager reconcile its share of the shared cluster's cost against the budget each month.
BB. Apply tag policies in Organizations that require a business-unit tag on every resource, and use the tag values to group the bill in Cost Explorer.
CC. Create one account per business unit and move the shared cluster into its own account, so that the account's cost is the cluster's charge-back.
DD. Create cost categories that map each unit's accounts and tags, and turn on split cost allocation data for EKS so the cluster's cost is split by namespace in the billing data.
Show the answer and explanation
Answer: D
A. Wrong: Budgets alerts warn when spend crosses a threshold, but they do not allocate the cluster's cost to the units. The reconciliation would be manual.
B. Wrong: Tag policies standardize tags on resources, but the shared cluster's EC2 instances run pods for all three units, so no single tag value describes their cost. The cluster's cost would stay in one undivided line.
C. Wrong: A separate account does not split the cost of the cluster among the three units, and the units still share the same cluster. The option creates a new allocation problem.
D. Right: Correct. Cost categories group the accounts and tags for each business unit, and split cost allocation data divides the shared EKS cost by namespace. The split appears in the cost and usage data, so finance needs no spreadsheets.
Explanation
Cost categories map each business unit's accounts and tags, and split cost allocation for EKS divides the shared cluster's cost by namespace in the billing data. Budgets, tag policies and a separate account each leave the shared cost unallocated.
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