Fullstack Engineer

As a Senior Fullstack Engineer, you own features end-to-end-from idea to prototype to production. You are responsible for delivering customer value directly through the product used by thousands of businesses across Europe., * Develop and maintain the platform using TypeScript, React, and Node.js (NestJS)

• Own features end-to-end: ideation, implementation, deployment, and iteration
• Work directly with customers through support, feedback, and user testing
• Translate real-world customer needs into scalable product features
• Continuously improve the Voice AI product in close collaboration with the team
• Contribute to future product and feature prioritization based on customer value, * Direct impact on a product used by thousands of companies across Europe
• 100% focus time (no regular meetings)
• Extremely fast execution pace with near-daily shipping
• Direct collaboration with founders and product leadership
• Continuous feedback from real production usage

• Strong experience building SaaS products with TypeScript, React, and Node.js (NestJS preferred)
• Proven ability to take full ownership of product features from concept to production
• Strong product thinking: focus on user value and impact, not just implementation
• Pragmatic engineering mindset: ability to break complex problems into simple, shippable increments
• Experience working directly with users or customers and incorporating feedback into product decisions
• Strong growth mindset with high execution speed
• Fluent German (required for Voice AI and DACH customer context) and strong English

• €80,000-€120,000 salary + equity
• 100% remote within the EU, with optional office in Vienna (7th district, meals included)
• Unlimited budget for tools when ROI is clear
• Access to modern AI tooling and high-performance engineering environment
• Fast-moving startup culture with strong ownership expectations

fonio.ai is an AI voice automation company building AI telephone assistants for small and medium-sized businesses. The product ensures that no business call is ever missed, helping companies stay responsive while focusing on what matters most. The vision goes beyond voice: fonio.ai is building toward the first fully automated, AI-native CRM system. With 7,500+ customers, €5M+ ARR, and ~30% monthly growth, the company is scaling fast toward a €30M ARR target by year-end, operating in a high-ownership, high-velocity environment.