Verify the provider API supports the promised property

Before a design doc promises an architectural property — reversibility, idempotency, exactly-once, cross-service atomicity, mechanical compensation, a sub-Xms SLA — verify the concrete AWS SDK method that mechanically guarantees it actually exists and supports the claim. "The Saga from the book" is not the same as "a Saga implementable on Cognito + Step Functions." AWS's own Saga docs admit the pattern gives eventual consistency, not ACID. For each promised property, demand the specific AWS API that backs it; if none exists, the property is NOT the system's and must be documented as "not mechanically guaranteed" or the design must change. Use at design review, whenever a …