Senior Frontend Developer

Cooperation Details

• Start date: As soon as possible, within 3-4 weeks

• 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

• 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.

• 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.

• 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.