---
issue: 098
title: "Backend: in-memory seenDeliveryIds resets on restart — webhook dedup lost"
severity: medium
domain: Payment
labels: [bug, backend, idempotency]
status: open
created: 2026-05-30
source: Full Codebase Audit 2026-05-30
---

# Backend: in-memory seenDeliveryIds resets on restart — webhook dedup lost

**Severity:** medium
**Domain:** Payment
**Labels:** bug, backend, idempotency

## Description

`requestNetworkRoutes.ts:16` maintains webhook deduplication via an in-memory `Set` of delivery IDs. This Set is lost on every server restart or pod restart. A redelivered webhook that arrived before the restart will be processed twice, potentially triggering double payment completion.

## Options

1. Persist processed delivery IDs in MongoDB (unique index) with TTL.
2. Use Redis SET with TTL for delivery-id dedup.
3. Make webhook handlers idempotent by keying state transitions on payment status guards.

## Recommendation

Persist delivery IDs (Mongo unique index or Redis) AND make handlers idempotent via status guards. This is an infra/state decision.

## Affected Files

- `backend/src/services/payment/requestNetwork/requestNetworkRoutes.ts:16`

## References

- [Full Codebase Audit 2026-05-30](../09%20-%20Audits/Full%20Codebase%20Audit%20-%202026-05-30.md) — DEC-36