Sr. Software Engineer, Frontend (UK)

Who We Are

At Firstup, our mission is to improve the employee experience at every moment that matters, large and small. As the communication pipeline for the world's workforce, we now serve 40 of the Fortune 100 companies, reaching and connecting more than 17 million employees daily. Our employees are experts in the employee experience, workforce communications and technology. Joining Firstup means joining a movement to make work better for every worker. As the world’s first intelligent communication platform, Firstup meaningfully engages employees at every moment from hire to retire, and delivers engagement insights to help companies support, promote and retain their talent. Our movement has taken root and is evident in our world-class customer base. Now we need your help. Ready to make a difference in the world?

Job Summary

The Sr. Software Engineer (FE) will lead the development of scalable, high-performance frontend architectures. You will drive engineering excellence through modern React patterns, robust testing strategies, and the strategic use of AI-assisted development tools to accelerate delivery without compromising quality.

Responsibilities

Core Engineering Build scalable frontend applications using modern React patterns and a component-driven architecture.

Systems Design Own the design and implementation of a reusable, accessible component library and documentation.

Testing & Quality Define the frontend testing strategy (Unit, Integration, E2E) including visual regression and user interaction coverage.

Performance & Reliability Optimize client-side performance and ensure production readiness through observability, error monitoring, and rapid incident resolution.

AI Integration Leverage and advocate for AI-assisted tools (e.g., GitHub Copilot, Claude) to accelerate development while maintaining rigorous engineering judgment and accountability for code correctness.

Leadership Drive team-wide best practices, conduct quality code reviews, and mentor engineers to elevate overall engineering quality.

Collaboration Partner with Product and Design to translate requirements into intuitive UI, making informed technical trade-offs in the face of ambiguity.

Minimum Qualifications

Experience

• 5+ years building reliable, high-performance frontend applications at scale.

Core Stack

• Expertise in React (Hooks, State Management), TypeScript, and modern tooling (Vite, Webpack).

Testing

• Proficiency with Jest, React Testing Library, and Cypress/Playwright.

UI/UX

• Proven experience building design systems or component libraries with a focus on WCAG accessibility.

AI Literacy

• Demonstrated ability to use and critically validate AI-assisted coding outputs (e.g., Claude, Copilot).

Education

• Bachelor’s in CS or equivalent practical experience.

Preferred Qualifications

Fullstack

• Experience with Ruby on Rails, Node.js, or AWS/Cloud infrastructure (Docker, Kubernetes).