Harnham
Senior Product Engineer
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Senior Product Engineer
London (Hybrid) | Up to £140,000 + Equity
Looking to make a genuine impact at an early-stage AI startup? This is an opportunity to join a well-funded business as one of its first engineering hires, taking ownership of a product already being tested by major enterprise customers.
The Company
This AI startup is building a behavioural intelligence platform that helps financial services organisations better understand customer behaviour and decision-making. Backed by significant early-stage investment, they are working with large enterprise clients and moving from proof-of-concept projects towards commercial deployment. With a small, highly capable team, they are focused on building scalable AI products with real-world impact.
The Role
You will take ownership of product development, helping to build and scale an AI-powered platform from an early stage.
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Responsibilities include:
- Building LLM-enabled products and features used by enterprise customers
- Designing and developing backend services, APIs, and platform capabilities
- Owning RAG workflows and AI application architecture
- Managing evaluation frameworks, testing, monitoring, and quality standards
- Optimising LLM performance, scalability, and cost efficiency
- Working closely with product leadership and customers to shape the roadmap
- Establishing engineering best practices across development and deployment
Your Skills & Experience
- Strong experience as a Product Software Engineer
- Proven track record building and shipping an LLM-based product from 0 to 1
- Experience owning architecture, product decisions, and implementation
- Strong backend engineering experience with API-first products
- Hands-on experience with RAG and production AI systems
- Understanding of token usage, model evaluation, and cost optimisation
- Ability to operate autonomously in a startup environment
- Strong communication and stakeholder management skills
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Desirable:
- Experience with Node.js, TypeScript, and React
- Computer Science background
- Experience within AI startups, technology companies, or financial services
What They Offer
- Salary up to £140,000
- Meaningful equity package
- Hybrid working in London
- Significant ownership and autonomy
- Opportunity to shape the engineering culture and technical direction
- Direct exposure to founders and business leadership
How to Apply
Apply today to learn more about this opportunity to build and scale cutting-edge AI products within a fast-growing startup.
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