Senior Fullstack Engineer

Project overview

We're looking for a Senior Full Stack Engineer who builds end-to-end features on a sports-training platform — and uses AI tools daily to ship faster. Coaches plan and assign training programs in a web console; athletes train from a mobile app. You'll work in a modern TypeScript codebase built on Next.js, Postgres in Supabase and Clerk, owning everything from the database schema and security policies to a polished UI. This is a hands-on product engineering role where AI is part of the daily workflow.

Key Responsibilities

Required Qualifications

Engineering:

AI Mindset & Tooling:

Product & Collaboration:

• Build and ship full-stack features end-to-end with TypeScript, Next.js 16 (App Router, Server Components, Server Actions) and React 19
• Design Postgres schemas in Supabase and secure them with Row-Level Security policies, migrations and generated types
• Implement auth and role-based access with Clerk (organizations, roles, permissions) integrated with Supabase RLS
• Build mobile-first screens for athletes and data-dense console screens for coaches with Tailwind CSS and shadcn/ui
• Keep domain logic in clean, testable services; write unit tests and integration tests against a local Supabase
• Deploy on Vercel and maintain infrastructure with Terraform
• Monitor and triage production issues with Sentry
• Use AI coding tools (e.g. Claude Code) daily to accelerate development
• Collaborate closely with product and design; participate in code reviews
• Senior: own features from idea to production, make and document architecture decisions, and mentor others
• 5+ years commercial experience
• Strong TypeScript and JavaScript fundamentals
• Hands-on experience with React and Next.js (App Router), including the server/client component boundary
• Solid SQL and PostgreSQL fundamentals: schema design, indexes, migrations
• Experience with authentication and authorization in web apps
• Understanding of Git workflows, CI/CD pipelines (GitHub Actions), and code quality tools (ESLint, Prettier)
• Comfortable working with automated tests and code reviews
• Regularly uses AI-assisted development tools (e.g. Claude Code)
• Reviews AI-generated code critically and knows when not to trust it
• Uses AI for real productivity gains, not just experimentation
• Understands the "why" behind features, not just the "how"
• Cares about UX, especially on mobile
• Comfortable working closely with product and design stakeholders
• Good English communication skills (written and spoken)

Nice to have

• Experience with Supabase and Postgres Row-Level Security
• Experience with Clerk authentication
• Terraform or other IaC experience
• Tailwind CSS and Radix UI / shadcn component libraries
• PWA and mobile web experience (iOS Safari, installability)
• Monorepo tooling (pnpm, Turborepo)
• Exposure to observability tools (Sentry, product analytics)
• Interest in sports, coaching or fitness products

Project details

• Start: flexible
• Remote: remote
• Location: Kraków, ul. Michała Żyszkowskiego, PL
• Rate: 20-25 EUR/h