Backend Software Engineer

• 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.
• Contribute to continuous product discovery, helping the team assess feasibility early and building quick technical prototypes to test ideas before we commit to building.
• Design, build and own Python backend services for our AI platform, from media upload through asynchronous ML processing to insight delivery.
• Work API-first and spec-driven, defining clean REST contracts that serve headless frontends, internal teams and customer integrations.
• Build MCP servers that make System1’s data and capabilities available to AI agents and tools, for customers and colleagues alike.
• Engineer through Claude Code day to day, building and sharing skills, subagents and workflows that raise the speed and quality of the whole team.
• Take code into production at scale with confidence, bringing the testing, observability and reliability our enterprise customers expect.
• Contribute to our infrastructure as code and cloud environment, understanding how your services are deployed, run and scaled.
• Work alongside our data scientists to bring models into production, learning the machine learning side of the platform as you go.
• Build with enterprise security and compliance in mind, so the world’s largest advertisers can trust the platform with their data.

• 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. You don’t wait for a perfectly specified ticket, you frame the problem 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, your code quality is as strong as your product thinking.
• 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.

To be successful in this role, you will have approximately 3–5 years of real-world software 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 backend services in Python.
• Experience designing and building REST APIs, ideally spec-driven, with a clear understanding of what frontends need from a headless architecture.
• Experience building SaaS software and taking code into production at scale, whether as part of a team or with personal responsibility for it.
• Hands‑on experience with at least one major cloud platform (e.g. AWS, Azure, GCP).
• A working understanding of infrastructure as code and the ability to contribute to it.
• Solid experience working with databases and data modelling.
• 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 building MCP servers, or a strong understanding of MCP and a drive to build with it.
• Experience…