Senior Full-Stack Engineer (TypeScript, React, Node.js)

About the role

A seed-stage B2B SaaS company is building subscription infrastructure for e-commerce: billing, checkout and developer tools. It needs a full-stack engineer who owns features from idea to release, working in a small team in Poland close to product and the founders. The position is hybrid in Warsaw.

Key responsibilities

• Build and ship full-stack features in TypeScript, with React on the frontend and Node.js on the backend.
• Own features end to end: clarify requirements, propose an approach, build, test, release and check the impact.
• Build merchant-facing subscription, billing and checkout flows that are clear and reliable.
• Improve the developer-facing side: APIs, docs, integrations, onboarding and error messages.
• Turn Figma designs into clean, accessible UI and suggest practical UX improvements.
• Keep the architecture simple, observable and maintainable, with no over-engineering.
• Do code reviews, write automated tests, keep documentation useful and use AI coding tools where they save time or improve quality.

Required profile

• Fluent Polish and residence in Poland.
• 5+ years of professional software engineering experience, mostly in product or SaaS companies, not only agencies or consulting.
• Experience taking at least one customer-facing feature from requirements to release.
• Comfortable working from Figma designs and independently in an early-stage team without detailed specs.

Required skills

• Strong TypeScript and Node.js in production, with features used by real customers.
• Production experience with React.
• Nice to have: Next.js or Vue and Nuxt; Fastify, Express or NestJS; payments and subscriptions (recurring billing, payment providers, invoicing, proration, dunning); e-commerce platforms such as Shopify, WooCommerce, Magento or headless commerce; public APIs, SDKs, webhooks or developer documentation; startup experience in teams under 200 people; hands-on use of AI and LLM tools (Cursor, Copilot, Claude, OpenAI).

Salary: $100,000 - $120,000 per year, full-time.