Frontend Software Engineer

Location: UK, remote with occasional travel

In the words of one of our senior clients recently…

“Market Research has changed more in the past 3 years, than in the previous 40”

About System1.

System1 is The Creative Effectiveness Platform. Our target customers are the world’s largest advertisers. We predict and improve marketing effectiveness. Our advertising and idea tests measure emotion to give our customers the most accurate predictions of the business impact of creativity.

To learn more about us, please visit System1 Group | Create with Confidence

About The Role

We are looking for a talented and ambitious Frontend Software Engineer to join the empowered product team building System1’s next-generation AI platform. As our first frontend engineer on the platform, you will shape how the world’s largest brands experience AI-powered predictions of their advertising’s effectiveness, building the interfaces through which they upload video at scale, explore analytics and insights, and work with AI agents.

You will work as a first-class member of the product team alongside your Product Manager, Product Designer and Team Lead to discover and deliver outcomes that matter to our customers and our business. This is a rare opportunity to define the frontend architecture and conventions from day one, engineer in a genuinely AI-native way, and work at the speed our market demands.

Are you energised by being a true partner in the product team, helping decide what to build, not just how to build it?

Do you already engineer through Claude Code every day, with your own skills and subagents, and the discipline to own every line you ship?

Are you excited by the challenge of making rich data, video and AI agents feel simple, fast and trustworthy for the people who use them?

Do you want to join us to excite and change the industry?

What will you be doing?

Partner as a member of an empowered product team (Product Manager, Product Designer, Team Lead and engineers), sharing accountability for the outcomes your team commits to.

Define the frontend architecture, patterns and conventions for our AI platform as our first frontend engineer, and set the bar for those who join after you.

Build the platform’s web application in TypeScript and React, creating fast, intuitive experiences for the world’s largest advertisers.

Bring complex analytics and insights to life through data visualisation and dashboards that make our predictions clear and actionable.

Build agentic and conversational interfaces, including streaming AI responses, that let customers work naturally alongside AI.

Create robust experiences for uploading, processing and reviewing video at scale.

Work API-first against a headless, spec-driven backend, consuming generated clients and helping shape the API contracts your interfaces depend on.

Partner closely with your Product Designer, iterating rapidly from prototype to production and building a component library and design system together.

Put automated testing at the heart of everything you ship, with a fully automated CI/CD pipeline that lets the team release with confidence.

Engineer through Claude Code day to day, building and sharing skills, subagents and workflows that raise the speed and quality of the whole team.

Contribute to continuous product discovery, helping the team assess feasibility early and building quick prototypes to test ideas with customers before we commit.

You need to be this kind of person

• A missionary, not a mercenary. You care deeply about the customer problem and the outcome, not just the code.
• Outcome-driven. You measure your success by the change you create for customers and the business, not by tickets closed.
• An engineer first, with AI as a force multiplier. You use AI tools to move faster with rigour, not to skip the thinking.
• Comfortable with ambiguity and ownership. As our first frontend engineer, you don’t wait to be told how things should be done, you shape it with your team and go.
• A clear communicator, able to explain technical trade-offs to product, design, data science and commercial colleagues as well as to fellow engineers.
• Curious and a lifelong learner, with the integrity to back your point of view with evidence in front of colleagues, customers and stakeholders.
• Able to see the bigger picture without losing attention to detail, you care about the pixels and the performance as much as the architecture.
• A natural collaborator, comfortable working with all departments at all seniorities, and equally able to drive work forward independently.
• Passionate about (good!) advertising, how it works and how it can be improved or excited to become so.

You need to have the following experience

• To be successful in this role, you will have approximately 3–5 years of real-world frontend engineering experience and be ready to operate as a first-class member of an empowered product team, where you’ll have outsized influence on the outcomes we deliver.
• Strong commercial experience building web applications in TypeScript with React or another modern component-based framework.
• Experience building data-rich interfaces, with a strong track record in data visualisation, dashboards and presenting analytics and insights.
• Experience building conversational or agentic interfaces, including handling streaming responses from AI models.
• Experience building against headless, API-first backends, ideally consuming clients generated from API specifications.
• A testing-first mindset, with hands-on experience of automated testing and fully automated CI/CD pipelines.
• Experience working closely with designers in fast, iterative cycles, and building or contributing to a component library or design system.
• Daily use of Claude Code as an engineering tool, including building your own skills and subagents, with an engineering-led approach rather than vibe coding.
• Experience working in a product operating model, as part of an empowered, cross-functional product team.
• Experience of building accessible interfaces to recognised standards (e.g. WCAG).
• Experience with video upload, playback or media-heavy applications at scale is a strong plus.
• Familiarity with cloud platforms and the security and compliance expectations of enterprise customers is a plus.
• This role will require you to operate across multiple discovery and delivery threads in parallel, balancing speed with the craft and reliability our customers expect.

Benefits

We offer a competitive salary and bonus scheme, including health insurance, and pension. Our people are important to us, and we understand that each person has a life outside of work and we therefore offer flexible, remote working within the UK, with occasional travel to get together for company and team meet-ups. We also offer several wellbeing resources such as “de-clutter” afternoons for your personal and professional needs.

We encourage learning and offer education reimbursement opportunities.

We have recognition schemes, and regular socials, including summer and winter parties!

We welcome applicants from all diverse communities and encourage our candidates to ask us about reasonable adjustments that we may be able to make to support through our recruitment process and while in post.