Senior/Staff Software Engineer, AI in London

About Engineering at Fonoa

Engineering is central to how we build the business. We focus on solving real customer problems, not just shipping features. We work in small, high-trust teams, with full ownership across the lifecycle, from design to production and beyond.

We value:

• Ownership – engineers own what they build end-to-end
• Simplicity – we break down complex problems into clear solutions
• Thinking Big - we innovate with modern technologies (LLMs, AI Agents, etc.) to solve meaningful problems
• Quality – scalable, maintainable systems are non-negotiable
• Speed & iteration – we ship fast, learn, and improve continuously
• Collaboration – we win as a team, not as individuals

Position Overview

As Fonoa continues to evolve its product capabilities, we are looking for a Senior or Staff Software Engineer to help us build AI-powered experiences that feel deeply integrated into the product, not layered on top of it. This is not a role focused on experiments disconnected from production. You will work on real customer-facing systems, building intelligent workflows, natural language interfaces, and agent-driven experiences that make complex problems simpler for our users and internal teams.

You’ll work closely with engineering, product, and design to prototype, iterate, and scale new AI capabilities across the platform. This includes everything from designing backend systems that power AI workflows to shaping model behaviour, evaluation pipelines, and agent orchestration.

We are still early in this journey, which means this role requires someone who is comfortable operating in ambiguity, experimenting quickly, and helping define how AI is applied across products and workflows. We are looking for engineers who combine strong product instincts with deep technical understanding, and who are excited about building practical AI systems that deliver real value.

This is a highly collaborative, hands-on role for someone who enjoys owning problems end-to-end, moving quickly, and building systems that balance product experience, reliability, scalability, and long-term maintainability.

What You Will Do

• Build AI-powered product features that feel native, fast, and intuitive to use
• Partner closely with product and design to prototype and iterate on intelligent workflows and user interactions
• Design backend services powering natural language interfaces, smart suggestions, and agentic systems
• Optimize prompts, shape model behaviour, and improve evaluation pipelines
• Build and evolve internal and external agent platforms
• Enable both technical and non-technical teams to leverage AI more effectively
• Continuously experiment, iterate, and improve AI systems in production

What We’re Looking For

• 5+ years building customer-facing products at a high-quality software company
• Strong track record of delivering complex, end-to-end product features with visible impact
• Ability to shape problems and drive solutions independently with high ownership
• Deep understanding of LLMs, prompt engineering, agent frameworks, and AI safety/security practices
• Experience with RAG architectures and model evaluation
• Strong product and engineering instincts, with the ability to balance speed, quality, and pragmatism
• Comfortable operating in fast-moving, ambiguous environments
• Proven ability to experiment and deliver in an evolving technology landscape

API Documentation

For engineers, API design and structure are an important part of evaluating a role. You can explore our API and how we build products here: https://docs.fonoa.com/

Tech Stack

We use these technologies today, but we don’t hire for specific tools. We care about engineers who can understand problems, make good technical decisions, and choose the right tools for the job.

• Backend: Node.js, Go
• Frontend: React, TypeScript
• Infrastructure: GCP, k8s, Terraform, Postgres

Note: If you don’t think you have the full experience we’re looking for, but you could be a fit and are willing to learn, do apply anyway! We are building a diverse and inclusive team.

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