Senior Founding Engineer

Arrows; Greater London; On-site; GBP 120,000 - 150,000; Full time

Job summary

Arrows is seeking a senior software engineer to own the core infrastructure behind its AI product, delivering reliable APIs and clean interfaces essential to a fast-growing platform. You’ll work end-to-end across the stack, from database to frontend, and ship features that endure as the product evolves.

You’ll own the agentic layer, building UI and APIs that consume sub-agent outputs directly, and you’ll use AI tooling daily to plan, write, review, and ship faster in a high-agency environment.

Qualifications

• 8+ years of professional software engineering experience with end-to-end ownership.
• Proficiency in UI, API and database development with strong TypeScript and React in production.
• Daily use of AI tooling as part of the workflow.

Responsibilities

• Feature delivery end-to-end, from database to frontend, across most parts of the stack.
• Maintenance and quality work, refactoring as the product evolves and raising the bar for users.
• Handle ambiguous work and pick up tasks as needed, without waiting for direction.
• Develop the agentic layer, building UI and APIs that consume sub-agent outputs.
• Define and optimize your own workflow with AI tooling to ship faster.

Skills

Full-stack development

TypeScript

React

AI tooling

Agentic systems

End-to-end ownership

Production readiness

Tools

LLM tooling

Job description

A well-backed, early-stage AI company is hiring a senior engineer to own the core infrastructure behind its AI product: reliable APIs, clean interfaces, and the kind of engineering that keeps a fast-growing product stable.

You're the generalist anchor on a small team. You build features end-to-end, from the database to the React component, and you live with what you ship rather than handing it off. You work directly with the company's agentic systems, not just alongside them, consuming sub-agent outputs and building the APIs that route between them. You're senior enough that the answer to "who owns this?" is often "whoever notices it first" if you see a problem, the path to fixing it is short.

What you'll own:

• Feature delivery end-to-end, from database to frontend, across most parts of the stack most weeks.
• Maintenance and quality, fixing and refactoring what you ship as the product evolves, and raising the bar before users hit the rough edges.
• Ambiguous work, picking up whatever needs doing rather than waiting to be assigned.
• The agentic layer, building UI and APIs that consume the company's sub-agent outputs directly.
• Your own workflow, using AI tooling daily to plan, write, review and ship faster.

What we're looking for:

• 8+ years' professional software engineering experience, ideally built at one or two companies rather than spread thin, so you've owned systems end-to-end and lived with the consequences.
• Full-stack fundamentals, comfortable across UI, API and database with strong TypeScript and React in production.
• Genuine AI fluency, daily hands-on use of AI tooling as part of how you already work, not occasional exposure.
• Production agentic experience, hands-on with agentic systems or LLM-powered features that real users depend on.
• High agency, operating with very little oversight and a track record of shipping and maintaining software people rely on.

For more information: [e-mail]