Sthenos AI is the AI developer of EFA Group, building intelligent, mission-ready solutions for defense and aerospace. With deep expertise in Command-and-Control (C2), cyber defense, computer vision, and autonomous systems, we design and deploy secure, field-proven AI that enhances operational efficiency and situational awareness. As part of a leading European defense ecosystem, we bring scalable innovation where it matters most - in the theater of operations.

As a Senior Frontend Engineer (w/m/d), you will translate product and UX designs into high-quality, maintainable code using TypeScript and React. You’ll build user interfaces that are performant, accessible, and reliable, especially under the realities of AI systems (latency, streaming results, partial data, uncertainty, and frequent iteration). You will collaborate closely with the UX Designer, ML Engineering and Site Reliability Engineering to deliver UI experiences that feel seamless and robust in production:

• Implement UX designs in React + TypeScript with high fidelity, turning prototypes and component specs into production-ready UI.
• Build scalable UI architecture: component libraries, design-system alignment, state management patterns, and reusable abstractions.
• Create data-intensive, AI-aware interfaces: handle streaming inference, pagination, large tables, timelines, overlays, and multi-panel workflows while keeping UX responsive.
• Engineer for performance: optimize rendering, loading strategies, caching, and bundle sizes; ensure smooth interaction even on heavy screens.
• Ensure reliability in real-world conditions: resilient error states, graceful degradation, offline/limited connectivity considerations where relevant, and clear recovery paths.
• Quality and testability: write unit/integration tests; maintain CI-friendly test suites; prevent regressions in key flows.
• Collaborate on UX handoff and iteration: work tightly with the UX Designer to refine interaction details and propose implementation-aware improvements.
• Integrate with APIs and platforms: connect UI to backend services (REST/GraphQL/gRPC where relevant), authentication/authorization, and operational tooling.
• Observability and operability: collaborate with SRE to instrument frontend telemetry (errors, performance metrics, user flow signals) and support incident-friendly debugging.
• Accessibility and inclusiveness: implement keyboard support, focus management, semantic HTML, and accessible components as part of “definition of done.”
• Maintain engineering standards: code reviews, documentation, and consistent patterns across the frontend codebase.

Your skills

• Strong professional experience building production web applications with React and TypeScript.
• Excellent command of modern frontend fundamentals: component architecture, state management, async data flows, browser performance.
• Solid understanding of HTML/CSS (responsive layouts, design tokens, component styling approaches).
• Background in working with UX Designers and consuming information from design and prototyping tools like Figma and Banani.
• Experience integrating UIs with backend APIs and handling auth, permissions, and secure data presentation.

Nice to have

• Strong experience implementing or contributing to a design system (Storybook, component libraries, token pipelines).
• Experience with observability tooling and frontend performance monitoring.
• Exposure to AI product interfaces (uncertainty/confidence visualization, explanations, human-in-the-loop workflows).
• Familiarity collaborating with SRE on reliability practices and incident response for user-facing systems.

Your competencies

• Craft + pragmatism: you care about details, but you ship by balancing fidelity, performance, and maintainability.
• Product thinking: you understand what users need and proactively improve implementation choices to support them.
• Engineering ownership: you take responsibility for UI quality in production across different platforms (not just “it works on my machine”).
• Collaboration: you communicate clearly with UX, ML, DS, and SRE, and align quickly on trade-offs.
• Consistency and scalability: you build patterns others can reuse and extend without fragile complexity.

We Offer

• Competitive remuneration package
• Private medical insurance package
• Continuous learning & development opportunities
• Participation in cultural and team-building activities
• Exposure to a growing environment with cutting-edge technologies
• Corporate wellness initiatives