Senior Node.js Engineer for Billing & Job-Queue Audit (Stripe + BullMQ/Redis)

I run a SaaS platform with a credit-based billing system and a background job queue. Before a major traffic push, I need an experienced engineer to audit and harden the money and job paths so nothing breaks at scale. The stack: Node.js, Stripe (credit ledger), BullMQ with Redis, Railway hosting. What I need: Audit the Stripe credit ledger for race conditions, double-spend, and silent credit burns Audit the BullMQ/Redis flow for stuck, duplicated, lost, or corrupted job states Fix what you find, with idempotency and transactional safety on all billing and job operations Build and run a load test to confirm integrity at high concurrency Deliver a short written report: what was broken, what you fixed, remaining risks Scope and terms: Fixed-fee project, roughly 1 to 2 weeks You work in staging with anonymized data, no production or live payment keys NDA required before any access to the codebase To apply, do not send a generic pitch. Tell me about a specific time you fixed a race condition or idempotency bug in a payment or queue system, and how you reproduced it. That tells me more than a resume. This is an audit-first engagement. If it goes well, there may be more work.