Freelance Full-Stack Developer (Node.js/TypeScript) — Legacy Stabilization + Credit Notes & SEPA Payout Export

The system is live and functional but historically grown, with structural/code-quality issues, missing validations, security gaps, and manual operational workflows. Your mission: stabilize the platform, make the codebase maintainable, and implement reliable financial workflows for credit notes (Gutschrift) and payout preparation via SEPA pain.001 XML exports (manual upload in the client’s bank portal — no direct payment execution). Scope / Responsibilities 1) System audit & stabilization Understand an existing Node.js/TypeScript codebase quickly Identify, reproduce, and fix bugs in a structured way Improve logging, error handling, and observability Harden APIs (validation, rate limits where needed) and secure sensitive routes (uploads, workers) Ensure strict multi-tenant isolation (companyId/orgId) across the system 2) Credit Notes (Gutschrift) — end-to-end implementation Implement a clean, status-driven credit note process (e.g., draft → posted) Validation of inputs and domain rules Auditable data flows (traceability of “why/how a credit note exists”) Integrate into existing API/worker flows and dashboard 3) Payout preparation & SEPA export Generate payout proposals from posted credit notes (idempotent, no duplicates) Validate bank data (IBAN) + business rules Create SEPA pain.001 XML export batches for bank portal upload Track export history + statuses (exported/paid), with an MVP “mark as paid” workflow Design for future reconciliation (optional) Tech Stack Node.js + TypeScript Backend: Express / NestJS / [login to view URL] API routes (existing system) Validation: Zod (or similar) Queue/Jobs: BullMQ/Redis (or similar) Cron/Scheduler DB: existing (Prisma) SEPA XML generation (pain.001) Requirements Strong experience with Node.js/TypeScript in production systems Comfortable working in legacy/historically grown codebases Solid understanding of: API security & validation background jobs/queues and retry patterns multi-tenant architectures financial workflows (status machines, auditability, idempotency) Implementation SEPA / payments / XML export experience Experience with reconciliation workflows (bank statements/camt files) CI/CD + testing mindset (unit tests / 1–2 E2E flows)

Project ID: 40192130