Senior Fullstack Engineer

About the Role This is a Senior Fullstack Engineer position at a fast-growing, seed-funded European AI voice technology startup serving thousands of SMEs. You will own features end-to-end, from prototype to production, and directly shape the product experience for a German-language AI phone assistant used across Europe. What You'll Do Take full ownership of features across the entire stack, from architecture decisions through implementation and release. Engage regularly with customers, partners, and the Sales team to identify real pain points and inform priorities. Run product discovery by forming hypotheses and validating them quickly through lightweight experiments. Instrument your areas of ownership with the metrics needed to make data-driven decisions. Build pragmatic, scalable software that balances immediate customer value with long-term maintainability. Communicate asynchronously and keep meeting overhead low, prioritizing shipping. Act with radical ownership, pushing initiatives forward proactively. What We're Looking For 5 or more years of fullstack engineering experience with end-to-end delivery responsibility for customer-facing web applications. Strong hands-on experience with Node.js, TypeScript, NestJS, and React . Proven ability to drive product discovery: forming hypotheses, running experiments, and measuring outcomes. Experience identifying, collecting, and using metrics to support product decisions. Comfort collaborating directly with customers, partners, and sales to extract actionable insights. Native-level German proficiency (required, given the product's language focus). Fluent English for team communication. Strong CS fundamentals and sound judgment when trading off speed, quality, and effort. Experience integrating LLMs (such as OpenAI APIs) into production applications is a strong plus. Familiarity with GDPR and EU AI Act considerations for AI services is a plus. Experience working in a high-growth startup environment is a plus. Compensation & Benefits Salary range: 80,000 to 120,000 EUR annually . Visa sponsorship is not available for this role. Location Fully remote, with a preference for candidates based in Germany or Austria and availability during Central European Time hours. Optional in-person collaboration from the Vienna, Austria office is available.