Senior Frontend Developer

Cooperation Details
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Start date: As soon as possible, within 3–4 weeks

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Contract duration: 12 months initially, with possible extensions
• Contract type: B2B
• Working model: Hybrid, with 2 days per week from the Warsaw office and the remaining days remotely

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Equipment: Laptop provided by the client

• Travel: Up to one possible business trip per year to the Netherlands or France (paid by the Client)
• Languages: fluent Polish and English are a must

We are looking for a Senior Frontend Developer to join a new initiative delivered for an international client operating in the information services sector.
Both projects are greenfield initiatives developed from scratch. Each team will consist of approximately five people, including a Tech Lead, Backend Developer, Frontend Developer, and QA Engineer.

Responsibilities

• Developing frontend applications using React and TypeScript.
• Building advanced enterprise-grade user interfaces, including dashboards, forms, filters, cards, and drill-down views.
• Integrating frontend applications with APIs using a contract-first approach.
• Designing and developing reusable components and solutions based on a design system.
• Ensuring accessibility, responsiveness, performance, usability, and overall application quality.
• Implementing explainability-focused UI patterns, including evidence, rationale, confidence levels, and source traceability.
• Building human review workflows that support approval, rejection, and manual override of system recommendations.
• Collaborating closely with the Tech Lead, Backend Developers, QA Engineers, and other team members.
• Contributing to component, UI integration, and regression testing.
• Working according to spec-driven development, API-first, and event-driven delivery principles.
• Ensuring auditability, traceability, and explainability by design.
• Supporting thin vertical slice and steel-thread delivery to validate end-to-end functionality early in the development process.

Requirements

• Senior-level experience in frontend software development.

• Strong practical knowledge of React and TypeScript.
• Experience in building complex enterprise-grade applications and user interfaces.
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Hands-on experience with API integration.

• Familiarity with contract-first or API-first development.
• Experience in creating reusable components and working with design systems.
• Good understanding of accessibility, responsive design, performance optimisation, and usability.
• Experience with frontend components, integration, and regression testing.
• Ability to work effectively in a cross-functional product team.
• Strong quality and validation mindset from the beginning of the development lifecycle.
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Fluency in Polish and English.

Experience in projects involving AI, agentic workflows, human-in-the-loop governance, explainability, or decision-support systems will be considered an advantage.