Well-Architected architecture study
Resilient Serverless Checkout
A transactional workload design that protects checkout from duplicate requests, partial failures, downstream latency, and public abuse.
AWS
Customer checkout
L
Lambda order API
Lambda
DDB
DynamoDB orders
DynamoDB
SQS
SQS + EventBridge
SQS
SNS
Fulfillment and notification workers
SNS
Problem
Checkout workloads need to handle retries, duplicate submissions, payment uncertainty, downstream failures, and abuse without losing orders or charging users twice.
Design
- AWS WAF and API Gateway protect the public boundary.
- Lambda validates carts and uses an idempotency key for order creation.
- DynamoDB stores order state with conditional writes.
- SQS buffers downstream fulfillment steps.
- EventBridge publishes domain events to notification, inventory, and analytics consumers.
- CloudWatch alarms watch error rate, queue age, and failed state transitions.
Well-Architected lens
- Reliability: idempotency, conditional writes, queues, retries, and DLQs.
- Security: WAF, scoped IAM, input validation, and no card data stored in application tables.
- Performance efficiency: asynchronous downstream work keeps checkout latency low.
- Operational excellence: state transition metrics and runbooks for stuck orders.
Why it is not live here
A believable checkout system needs payment-provider mocks, load tests, fraud controls, and operational procedures. A public portfolio version would invite unnecessary complexity and abuse risk.