An architecture review with a cost section checks, before an architecture is built or a service bought, that its running cost is estimated, understood and assigned to an owner. Much of the later bill follows from decisions taken at design time: services, regions, data paths, contracts. What the review does not ask turns up in the cost report, when only a rebuild can change the decision. This page covers the review as a process, its inputs, and the shorter procurement review for a new service or marketplace product. The trade-offs between architectures themselves are covered in architecture choices and cost.
How it works
The FinOps Foundation places the subject in its Framework under the Architecting & Workload Placement capability. From the Walk maturity level, the Framework expects the decision to rest on a written weighing in which cost sits beside value, sovereignty, resilience and sustainability, and the build to be held against it; at Run, gaps between the design and the system as built are tracked. The providers supply the questions.
| Provider | Tool | Cost questions |
|---|---|---|
| AWS | Well-Architected Tool with the Cost Optimization pillar | eleven questions, COST 1 to COST 11, among them service selection (COST 5), pricing models (COST 7), data transfer (COST 8) and evaluating new services (COST 10) |
| Azure | Azure Well-Architected Review, an assessment on Microsoft Learn | checklist CO:01 to CO:14, among them the cost model (CO:02), spending guardrails (CO:04) and environment costs (CO:08) |
| Google Cloud | Well-Architected Framework, cost optimisation pillar | no numbered questions but recommendations per principle; for a review, the cost awareness principle matters most |
AWS
The Well-Architected Tool documents a workload against the questions, counts high and medium risks and records milestones; AWS recommends saving one after every improvement. Custom lenses add your own questions, for an organisation's governance needs for example, and review templates pre-fill answers shared by several workloads. Three best practices carry the cost part: COST05-BP06 asks for a cost analysis at the usage expected over time, COST08-BP01 for a model of data transfer, whose cost on AWS depends on source, destination and volume, and COST07-BP03 for third-party agreements whose price grows only as your benefit grows.
Azure
The Azure Well-Architected Review covers reliability, security, operations and performance besides cost, and ends with recommendations. Central to the cost review is CO:02: a cost model estimating start-up and running cost, and a budget negotiated against it with room for the unplanned. CO:08 asks for spending to be prioritised across preproduction, production, operations and disaster recovery environments, with availability, licensing and operating hours considered per environment.
Google Cloud
Google advises teams to price each deployment option in their architecture blueprints, and counts projected resource costs at design and deployment time among the cost data every role needs.
Inputs to the review
| Input | Content | Provided by |
|---|---|---|
| Expected volume | users, requests, data volume per month, with a growth assumption | product |
| Estimate per option | pricing calculator or price API, noting whether list or contract prices were used | engineering |
| Data transfer paths | source, destination and volume of each connection | engineering |
| Commitment fit | whether existing commitments cover the new architecture | whoever buys commitments |
| Environments | test, staging and disaster recovery beside production | engineering |
| Exit and switching cost | data volume to move out, lock-in, termination fees | procurement |
| Owner and budget | who carries the cost, from which budget | cost owner |
| Checkpoint after go-live | what is compared with the estimate, and when | cost owner |
How the estimate is produced and what it cannot know is covered in shift left: cost checks before deployment; data paths are explained in data transfer and egress, commitment types in cloud commitment discounts compared by type. For exit cost, Article 29 of the EU Data Act (Regulation (EU) 2023/2854) requires providers of data processing services to give clear information, before a contract is signed, on standard service fees, early termination penalties and reduced switching charges; from 12 January 2027 they may no longer impose switching charges for the switching process, and the Regulation counts data egress charges among them. Planning for it is covered in EU Data Act: plan cloud switching costs before 2027; whether a given charge falls under it, legal counsel and procurement decide.
The procurement review
A SaaS service or marketplace product is often bought without an architecture change, so it needs a shorter review of its own with four questions: the term, with minimum commitment and termination; the billing path, meaning the cloud provider's invoice or the vendor's own (marketplace purchases on the cloud invoice); the data the vendor receives, checked by whoever handles data protection; and renewal, with its deadline and pricing rule. In AWS Marketplace, AWS is not a party to the agreement between buyer and seller. Since September 2026, private offers with contract pricing can include automatic renewal, with the price carry-forward and the decision deadline set by the seller. So that only reviewed products are bought, all three providers offer an approval layer: AWS Private Marketplace with approved catalogues per organisation, organisational unit or account; Private Microsoft Marketplace, where only approved partner offers can be deployed while Microsoft's own applications are always allowed; and Product Requests in Google Cloud, which turn a user's request into a procurement request to the administrators. Contract questions in detail are covered in procurement contracts and renewals.
The review ends with a decision and a name. Who signs at which size is set by the approval thresholds.
What it means for your cost
A review does not change the bill directly; it changes which costs surprise you. Its estimate becomes the baseline for the first full month; without it a variance has no reference point. With the checkpoint agreed in advance, a difference can be traced to a cause: different volume, data transfer nobody modelled, a discount the estimate left out. The outcome is recorded as described in traceability of cost decisions.
The review is not a one-off event. Under COST 10, AWS lists a review process per workload and regular reviews, and COST05-BP06 says the analysis effort should reflect the potential outcome. For a small company, a completed inputs table with a date and a signature covers most decisions; the thresholds decide when more is needed.
Where it goes wrong
- Reviews only when something happens. Symptom: cost questions come up only after an incident or a high bill, and every answer means a rebuild. Cause: no fixed checkpoint at design time; the FinOps Foundation places event-triggered reviews without a cadence at the Crawl level.
- An estimate without data paths. Symptom: the bill shows transfer between zones, regions or to the internet that the estimate does not contain. Cause: source, destination and volume of connections were not an input.
- List price against contract price. Symptom: estimate and actual cost differ consistently in one direction. Cause: the estimate uses list prices and the invoice negotiated prices, or the other way round.
- A stranded commitment. Symptom: a reservation's utilisation drops after a migration. Cause: commitment fit was never checked.
- A missed renewal deadline. Symptom: a marketplace agreement continues at a new price. Cause: automatic renewal was accepted with the offer, and nobody reviewed the renewal notice before the decision deadline.
- A catalogue that ignores existing subscriptions. Symptom: unapproved products keep running despite Private Marketplace. Cause: AWS Private Marketplace blocks new subscriptions and changes, not existing ones.
Sources
Read on 2026-10-16. FinOps Foundation Architecting & Workload Placement (CC BY 4.0); AWS cost optimization in the Well-Architected Framework, questions COST 5 to COST 8, questions COST 10 and COST 11, COST05-BP06 cost analysis for usage over time, COST07-BP03 third-party agreements, COST08-BP01 data transfer modelling, COST 10 evaluating new services, what is AWS Well-Architected Tool?, workloads, milestones, review templates, contracts in AWS Marketplace, auto-renewal for private offers, the announcement of 1 September 2026 and Private Marketplace; Microsoft Azure Well-Architected Review, Cost Optimization design review checklist and Private Microsoft Marketplace; Google Cloud cost optimization pillar, foster a culture of cost awareness and let your users request products; EUR-Lex Regulation (EU) 2023/2854 (Data Act).