Checkout v2: Idempotent payment webhooks

Owner: Angel · Draft 1 · Checkpoint 1

ACreated by Angel with Claude Code

Goal

Stop double-charging customers when the payment provider retries a webhook. Every payment.succeeded event must be processed exactly once.

Steps

1. 1.Add a processed_events table keyed by provider_event_id with a unique index.Add a processed_events table keyed by provider_event_id with a unique index and a 90-day expires_at column.DDeiber is editing this fragment withCodex
2. 2.Wrap the handler in a transaction: insert the event id first, then mark the order as paid.
3. 3.Return 200 immediately when the event id already exists. Count each duplicate in a metric.Return 200 immediately when the event id already exists. Count each duplicate in a metric and log its provider_event_id.AAngel is editing this fragment withClaude CodeShareCommentEdit with AIEdit selection with AISelected textReturn 200 immediately when the event id already exists. Count each duplicate in a metric.What should the agent change?Log every duplicate with its provider_event_idCancelLaunch

Open questions

Do we keep processed_events forever or expire rows after 90 days?MD1 / 1ResolveDo we keep processed_events forever or expire rows after 90 days?MMaría @maria · now
Expire after 90 days: it matches our retention policy.DDeiber @deiber · now
AAngel Agreed, 90 days works for me.Reply…Reply

DDeiber

MMaría

DDeiber · Codex

AAngel · Claude Code