Backend

The Inbox Pattern on AWS

ByAhmed Yassin5 min readJuly 10, 2026

Read full article

event duplicate (rejected) failure → DLQ

Stripe

Payment provider

API Gateway

Webhook ingress

Webhook Receiver

AWS Lambda

· verify signature· validate type· conditional PutItem

Webhook Inbox

DynamoDB

Payment Worker

AWS Lambda

EventBridge

PaymentSucceeded

Order Service

AWS Lambda

Orders

DynamoDB

Payments

DynamoDB

Failure Queue

SQS · DLQ

Webhook POSTconditional PutItemStreams · INSERT-onlypublishPaymentSucceededstatus = SUCCEEDEDretries exhaustedsame eventId → rejectedduplicate eventId → 2xx · ignored (no-op)⚠ dual-write gap
not atomic → Outbox (next post)

The Inbox Pattern on AWS: webhooks are deduplicated at the conditional write, drained in order by the worker, and fanned out through EventBridge - with the dual-write gap that the Outbox pattern closes next.