Frontend Engineer

Nostrion; Leusden; On-site; EUR 70,000 - 110,000; Full time

Job summary

Nostrion, based in the Netherlands, builds European AI for organisations handling sensitive information. As a Frontend Engineer, you’ll craft interfaces that transform complex AI and backend capabilities into clear, dependable workflows for professionals managing confidential documents.

You’ll collaborate with backend engineers, product stakeholders, and domain experts to shape frontend architecture, reusable components, and engineering standards, ensuring accessibility and performance across

Qualifications

• Proficient in building modern frontend applications with React and Next.js.
• Strong understanding of frontend architecture, state management, and API-driven apps.
• Experience with complex workflows, large documents, or data in products.
• Knowledge of authentication, authorization, and role-based access.
• Able to make informed technical decisions and explain trade-offs.
• Focus on usability, including loading states, errors, navigation, and clear feedback.

Responsibilities

• Design, build, and maintain frontend applications for Nostrion’s platform and Fidacta.
• Create intuitive interfaces for document search, AI assistance, document generation, and workflow automation.
• Help users inspect source material, review generated content, and understand system feedback.
• Build reusable components and interaction patterns for multiple products and sectors.
• Collaborate with backend engineers on API design, integration, streaming responses, and error handling.
• Implement authentication, permissions, and role-aware interfaces in a multi-tenant environment.
• Ensure applications are accessible, responsive, performant, and reliable.
• Take ownership of frontend architecture, tooling, code quality, and maintainability.
• Review code, support teammates, and make practical technical decisions.
• Work with product and domain experts to turn professional workflows into usable software.

Skills

React

Next.js

Frontend architecture

State management

APIs

Complex workflows

Data handling

Authentication & authorization

Decision making

Usability

Collaboration

Job description

At Nostrion, we build independent European AI for organisations working with sensitive information. Our platform helps professionals put their organisation’s knowledge to work while keeping control over their data, processes, and expertise.

European ownership, infrastructure, and governance are central to how we build. We combine open models with our own platform and work closely with domain experts to develop applications for regulated professions.

Fidacta, our solution for the notarial sector, makes this tangible. It helps notaries and their teams search private documents, obtain answers grounded in their own information, draft documents, and streamline everyday workflows. These are environments where confidentiality, accuracy, and professional judgement matter.

What You’ll Be Doing

As a Frontend Engineer, you build the interfaces that make these capabilities useful in daily practice. You turn complex AI and backend functionality into clear, dependable experiences for professionals handling sensitive documents and decisions.

Your work could help a user move from a question to its supporting sources, review a generated draft, or follow the progress of an automated workflow. You make it clear what the system is doing, what needs attention, and where the user remains in control.

You work closely with backend engineers, product stakeholders, and domain specialists. Alongside hands‑on development, you help shape frontend architecture, reusable components, and engineering standards.

Key Responsibilities

• Design, build, and maintain frontend applications for Nostrion’s platform and sector‑specific products, including Fidacta.
• Create intuitive interfaces for document search, AI assistance, document generation, and workflow automation.
• Help users inspect source material, review generated content, and understand system feedback.
• Build reusable components and interaction patterns that can support multiple products and sectors.
• Collaborate with backend engineers on API design, integration, streaming responses, and error handling.
• Implement authentication, permissions, and role‑aware interfaces for a multi‑tenant environment.
• Ensure applications are accessible, responsive, performant, and reliable.
• Take ownership of frontend architecture, tooling, code quality, and maintainability.
• Review code, support teammates, and make practical technical decisions.
• Work with product and domain experts to turn professional workflows into usable software.

What You Bring

• Strong hands‑on experience building modern frontend applications with React and frameworks such as Next.js.
• A good understanding of frontend architecture, state management, and API‑driven applications.
• Experience building products with complex workflows, documents, or substantial amounts of data.
• Familiarity with authentication, authorisation, and role‑based access.
• The ability to make technical decisions and explain the trade‑offs.
• An eye for usability, including loading states, errors, navigation, and clear feedback.
• A pragmatic approach: you take responsibility, work well with others, and deliver production‑ready software.

Bonus Points If You Have

• Experience building AI interfaces, conversational applications, or streaming user experiences.
• Experience with document editors, source references, version histories, or review workflows.
• Familiarity with design systems and reusable component libraries.
• Experience with frontend testing, accessibility, and performance optimisation.
• Experience working on SaaS products or software for regulated industries.
• Experience mentoring engineers or guiding frontend technical decisions.

Why This Role Matters

For the people using our products, trust is shaped by what they can see, understand, and verify. A useful interface helps them find relevant information, assess an answer, review a draft, and decide what happens next.

You will help make advanced AI practical for professionals whose work demands care, confidentiality, and accountability.

Eligibility & Application Information

We welcome non‑native Dutch speakers. To be eligible, you must:

• Have valid authorisation to work in the Netherlands.
• Reside in the Netherlands and be able to travel to the office.
• Be fluent in English. Dutch is not required.

Learn more at nostrion.com and fidacta.ai.