Freelance Full-Stack Developer (Node.js/TypeScript) — Legacy Stabilization + Credit Notes & SEPA Payout Export
Budget: $250 – $750 USD
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 / Next.js 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)
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 / Next.js 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)