Senior (6+ years) Full-stack Developer (Back-end focused)
Summary
Senior full-stack developer (back-end heavy) needed to build and scale fintech systems for a Warsaw-based agency. Requires 8+ years of experience, deep expertise in Node.js, PostgreSQL with migration-driven schemas and immutable double-entry ledgers, plus Next.js 16, TypeScript, React 19, and Stripe integrations. Finance and insurance domain knowledge is mandatory.
English B2+
A university degree in computer sciences.
Poland, Warszawa based candidates only.
Mandatory domain expertise in Finance and Insurance. Must understand financial logic and data integrity.
- 8+ years of experience in software development with a deep focus on Back-end architecture.
- Node.js
- Expertise in PostgreSQL and raw SQL: Experience working without ORMs, managing migration-driven schemas, and implementing immutable double-entry ledgers.
- Deep knowledge of Next.js 16 (App Router) and TypeScript: Proficiency in building scalable architectures using API route handlers and service layers in a Serverless environment (Vercel).
- Strong experience with modern Frontend: React 19 and Tailwind v4 (without heavy state-management libraries).
- Practical experience with Fintech integrations: Stripe payments, Auth.js (v5), and complex authentication (Passkeys, TOTP).
Will be a plus:
- Experience with Java
- Experience with AI/LLM integrations .
- Knowledge of regulatory compliance and security standards in Fintech/Insurtech.
- Experience with PDF generation (react-pdf / pdf-lib) and pluggable email provider layers.
- Experience in early-stage startups, moving from MVP to production-grade systems.
- Understanding of Node 24 features and modern web standards