Backend Developer — Bug Fixes, API Integrations & Complex Systems

The Role Debug and ship bug fixes in a complex system: points calculations, airline/payment API integrations, and agentic AI logic. Own features end-to-end with high code quality standards. Technical Stack Backend: Node.js + TypeScript, Supabase (PostgreSQL), REST APIs Frontend: Next.js 16, React 19 Testing: Vitest, Playwright Integrations: Stripe, 10+ airline/payment APIs, LLM APIs Ops: Vercel, Docker, GitHub CI/CD Requirements (Must Have) 4+ years backend development (solid fundamentals) Strong TypeScript and Node.js production experience SQL/relational database skills: write efficient queries, optimize indexes Testing mindset (Vitest, Jest, Playwright) Git and GitHub workflows (commits, PRs, code reviews) Fast debugging skills (Sentry, logs, DevTools) Fluent English (async communication) CET timezone (7am-6pm CET, plus or minus 2 hours flex) Willing to learn our unique platform (calculations, APIs, AI systems) Nice to Have Supabase/PostgreSQL, REST API design, Stripe experience, Vercel/serverless, AI/LLM integration (Claude, OpenAI), complex business logic, real-time systems, travel loyalty background What We're NOT Looking For Freelancers (short 3-month gigs) Developers uncomfortable with complexity Timezone mismatches "I'll figure it out as I go" attitude Your Submission Must Include Start with "Avios" (shows you read this) Timezone & Communication: State timezone, confirm CET availability, rate English level Portfolio (REQUIRED): 2-3 GitHub repos or deployed projects showing: A bug you fixed (problem and debugging approach) A feature you shipped (scope, approach, tests) Code quality (TypeScript, tests, clarity) Technical Questions (1-2 sentences each): How do you debug multi-system issues (database and APIs and business logic)? Experience with agentic AI/LLM APIs? How do you handle errors/retries? Time you optimized a slow system: what was your methodology? Real-time data sync experience across multiple systems? Complexity & Learning: Experience with complex business logic (calculations, financial systems, AI)? How do you approach learning a new complex codebase? Built/worked with agentic AI systems? Comfortable with real-time, integrated systems? Availability: Hours/week, notice period, can you start in 2 weeks? Learning: Supabase experience? Recent tech you learned? How you handle feedback? What We Offer Code ownership (own your features end-to-end) Weekly 1:1s and direct access to founders for architecture questions Learning budget, real impact (thousands of users weekly) Small team (3-5 engineers), flat hierarchy, async-friendly 6+ month contracts minimum Red Flags (Auto-Reject) Doesn't start with "AVIOS" No GitHub links or portfolio "Willing to learn TypeScript/Node.js" (you need to know this) No timezone confirmation Generic/templated proposal Less than 85% success rate Uncomfortable with complexity Interview Process Short Q&A (async, 24-48 hrs): 2-3 follow-up questions on your portfolio Technical Challenge (2-3 hrs async): Build a backend feature (e.g., Supabase webhook validator). Show your code quality and testing approach. Chat with Leads (30-60 mins): Discuss background, goals, codebase fit 2-Week Trial (optional): Work on real issues, see if it's a long-term fit Key Point This is NOT a junior role. You need 4+ years solid backend experience, strong fundamentals, and comfort with complexity. We're not teaching programming basics — we're looking for experienced developers ready to master a complex platform and ship fast. Questions? Ask in your proposal, but include all required sections.