Senior / Lead Developer - AI Platform in London

An AI scale-up is looking for a strong full-stack engineer to take ownership of its platform and lead where it goes next. They're London based, well-funded, and founded by people who have built and sold a business before. The product is already live with clients in MVP form, so you'd be joining something real and proven, with a clear mandate to take it to the next level.

The product ingests the messy, real-time behavioural signals of how people talk and behave across the internet, uses agentic workflows and LLM pipelines to turn that noise into rich, evidence-backed audience profiles, and then lets users test creative ideas against those profiles to predict what will land before a penny is spent. It is hard, applied AI with real commercial stakes: clients bet real budget on what it produces.

In practice that means working across several layers that each carry interesting challenges: large-scale data ingestion from social and web sources, an analysis layer that turns unstructured signal into structured, queryable audience intelligence, and an interface that makes all of it genuinely useful to non-technical users. It was built fast to prove the idea, and now needs proper engineering rigour to mature from MVP into a robust product.

What you'd do:

• Take ownership of the platform end to end and lead its technical direction as it grows.
• Build hands-on across the full stack, from the data and AI pipelines through to the product interface.
• Bring engineering rigour to a fast-built MVP: architecture, reliability, performance and the foundations to scale.
• Work with modern AI tooling day to day, building and improving the agentic workflows and LLM pipelines at the core of the product.
• Help shape product decisions and sit in conversations with the founders and clients, translating what the technology makes possible into clear value.
• Lead the AI function, with plans in place to grow and hire a team around you.

The tech:

• Front-end: React and Next.js, building interfaces that make complex AI output genuinely usable.
• Back-end: Node.js, building APIs and the server-side logic that ties data, AI services and product together.
• AI layer: hands-on with LLMs and agentic workflows, using modern AI APIs, retrieval pipelines and orchestration.
• Data: ingesting and making sense of large volumes of unstructured, real-time signal from across the web and social platforms.

They care more about a strong full-stack builder who is genuinely deep in AI than about a checklist of exact technologies. If you have built real things with this kind of stack and these kinds of AI tools, that's what matters.

Who it suits:

• A strong full-stack engineer, comfortable owning both the front-end and back-end of a product.
• Someone with real, hands-on experience building with AI: LLMs, agents and modern tooling, not just an interest in them.
• A builder with a bias to ship, comfortable with ambiguity and the pace of an early-stage product.
• Someone who enjoys the product and people side too: shaping what gets built, and being able to explain it to founders and clients.
• Ideally experience in a startup or small, fast-moving company, where you've worn several hats.

Why it's worth a look:

• You own a real, live product rather than inheriting a mature codebase or starting from a blank page.
• Genuine influence: the founders are excellent commercially but aren't engineers, so the technical and AI direction is yours to lead.
• Hard, current AI work with real commercial impact, using the best tooling.
• Leadership from the start, with a path to build and run a team as the company scales.
• Share options in a well-funded company with founders who have built and sold before.

The details:

• London based, hybrid.
• Salary up to £120k, with flexibility to go higher for the right person, plus share options.
• This is a senior role with leadership scope and real ownership from day one.

If it sounds of interest, get in touch and I'll share the full details.