You will own the end-to-end development of AI-driven features for an executive assistant platform growing from £1M to £17M ARR in ten months. Operating without product managers, you'll architect RAG systems and fine-tune LLMs to automate complex workflows for 180,000+ users at global enterprises like Starbucks and TikTok.
Back to all jobs
Find a job withJack
This job is no longer actively hiring. Open Roles to see active jobs.
London, United KingdomNot Disclosed + Equity
Product Engineer at Fyxer AI - Series B AI startup
Join Fyxer AI, the Series B startup redefining productivity as the 7th ranked AI app globally. Having exploded from £1M to £17M ARR in under a year, they are seeking a Product Engineer to own core AI features for 180,000+ users. You'll build production RAG systems and agentic workflows in a high-autonomy environment with no PMs or bureaucracy. Backed by Madrona and Marc Benioff, Fyxer offers founding-level equity and a chance to work alongside elite engineers from Oxford and MIT. If you're a high-velocity builder ready to scale a category-defining AI assistant, this is your next move.
Overview
Role overview
Company
Fyxer AI
SoftwareLondon, United KingdomSeries B (VC-backed)
Fyxer AI - Series B applied AI startup backed by Madrona and Marc Benioff
Backed by Madrona, Lakestar Capital, 20VC, 20Growth, Marc Benioff.
Responsibilities
What you will do
- Design and deploy production RAG systems and multi-agent AI orchestration to manage 50,000+ inboxes and automate meeting follow-ups.
- Develop LLM fine-tuning pipelines using Python and open-source models to replicate individual user voices and professional tones accurately.
- Lead full-stack feature development from discovery to deployment using TypeScript, React, and Next.js, shipping high-impact updates in weekly cycles.
Candidate profile
Who this is a fit for
- Proven "builder DNA" with experience as a founder or early-stage engineer who has successfully shipped 0-to-1 products in fast-paced environments.
- Deep technical expertise in shipping production AI systems, including RAG pipelines, vector databases, and fine-tuning models like Llama or GPT.
- Exceptional full-stack proficiency in TypeScript and Python, ideally coming from a high-velocity background like OpenAI, DeepMind, or a breakout Tier-1 startup.
What makes it remarkable
Why this role is remarkable
- Join one of Europe’s fastest-growing AI companies, ranked 7th in Andreessen Horowitz’s list of top AI apps with a forecasted $100M ARR by 2025.
- High-autonomy environment with no professional managers or bureaucracy, offering the highest cash and equity packages in the London market for founding-level talent.
- Work directly with Oxford/MIT founders and a lean team of 12 elite engineers to define the category of proactive AI executive assistants.
Jack & Jill
How Jack & Jill work together
I get to know what you’re great at, then find roles you’d never find yourself.Ok, I'll go first. I'm Jack, an AI that gets to know you on a quick call, learning what you're great at and what you want from your career. Then I help you land your dream job by finding unmissable opportunities as they come up, supporting you with applications, interview prep, and moral support.
I recruit from Jack’s network and make the intro when I spot a great match.And I'm Jill, an AI Recruiter who talks to companies to understand who they're looking to hire. Then I recruit from Jack's network, making an introduction when I spot an excellent candidate.
Meet Jack
Jack gets to know what you're great at and what you want next, then searches 14 million jobs daily and introduces you directly to hiring managers.
How does this work?
Jack's an AI agent for job searching and career coaching. He works for you.
Jill is the AI recruiter working for the company. She recruits from Jack's network.
If it's a match and the company wants to meet you, they'll make the intro. In the meantime, if you'd like, Jack will send you excellent alternatives.
Jack