# Step 0 — approved requirements specification

## Workflow request

Produce a reviewable, deployable Google Cloud reference architecture for an event-driven order-ingestion service, while separating product-neutral discovery from product selection and validating IaC without provisioning.

## Functional requirements

- Accept authenticated order submissions over HTTPS.
- Validate order payloads and return a synchronous acknowledgement.
- Process accepted orders asynchronously so ingestion is not coupled to downstream latency.
- Persist durable order state and support transactional updates.
- Store credentials and other sensitive configuration outside source code.
- Provide application logs, metrics, traces, and auditable administrative activity.
- Support repeatable infrastructure deployment from version-controlled IaC.
- Provide a documented rollback and dead-letter/replay approach.

## Non-functional requirements

- Target 99.9% monthly availability for the public ingestion endpoint.
- Target p95 acknowledgement latency below 500 ms under the expected baseline load.
- Provide encryption in transit and at rest.
- Scale horizontally for bursty traffic and isolate asynchronous work from ingestion.
- Apply least-privilege identities and private access to data services where practical.
- Retain operational and audit evidence for at least 90 days, subject to organizational policy.
- Ensure deployments are reproducible, reviewable, and non-destructive by default.

## Constraints

- The target platform is Google Cloud.
- Terraform is the infrastructure-as-code language.
- No resources may be provisioned during architecture validation.
- Product selection is explicitly deferred until this requirements section is approved.
- The first release is a reference implementation, not a completed compliance certification.
- Region, budget, traffic volume, data residency, and regulatory classification are not yet supplied.

## Assumptions

- Orders are JSON and contain an immutable order identifier.
- A single primary region is acceptable for the initial release.
- The service can tolerate eventual consistency for asynchronous fulfillment.
- A managed relational database is appropriate for transactional order state.
- CI has permission to run Terraform formatting, initialization without a backend, validation, and an optional credentialed plan.
- Application container images are published by a separate build pipeline.

## Open questions

- What are peak requests per second, payload size, and daily order volume?
- Which identity provider and client authentication protocol are required?
- What RTO/RPO and disaster-recovery region are required?
- What data residency, PCI, GDPR, or other controls apply?
- Should the database be regional or cross-region, and what is the retention/deletion policy?
- Which downstream systems consume orders, and what delivery semantics do they require?
- What is the approved Google Cloud project, region, DNS zone, and naming convention?
- What are the maximum monthly budget and alerting escalation targets?

Product selection deferred during this step: **true**.