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# Senior AI Software Engineer

- **Company:** Harnham
- **Location:** London, UK
- **Experience:** Expert
- **Salary:** £120,000.0 - £140,000.0
- **Contract:** Permanent contract
- **Skills:** Artificial Intelligence, Amazon Web Services, Software Quality, PostgreSQL, Node.Js, TypeScript, Web Applications, ReactJS, Retrieval-Augmented Generation, Large Language Models, Caching, Machine Learning Operations, Api Design
- **Published:** October 6, 2026
- **Apply:** https://www.reed.co.uk/jobs/senior-ai-software-engineer/57424341

## About the Role

* Experience building and scaling production LLM-powered applications
 * Strong full-stack engineering background
 * Experience delivering secure, reliable and scalable systems
 * Comfortable working across multiple technologies and learning new stacks quickly
 * Experience with React and modern web applications
 * Product-minded approach with the ability to operate autonomously
 * Passion for building in an early-stage, high-growth environment
 * Experience within regulated industries or financial services is beneficial but not essential

## Description

We're partnered with a fast-growing AI start-up building cutting-edge behavioural intelligence technology for the financial services sector. Backed by an exceptional leadership team and industry experts, they're developing a platform that helps organisations better understand client behaviour through advanced AI and large language models.

As their first senior individual contributor engineering hire, you'll play a critical role in shaping both the product and engineering culture from the ground up.

The Opportunity

This is a true 0-to-1 product engineering role. You'll work closely with senior leadership to build and scale a greenfield product, taking ownership across the full stack while driving the architecture and evolution of production-grade AI systems.

You'll have significant influence over technical direction, engineering standards, product decisions and future hiring as the team grows.

What You'll Be Doing

 * Building and shipping customer-facing product features end-to-end
 * Developing and scaling production LLM applications
 * Owning RAG pipelines and AI application architecture
 * Implementing guardrails, evaluations, caching and model routing strategies
 * Working across TypeScript, React, Node.js, PostgreSQL and AWS (Open to different technology backgrounds!)
 * Building API-first services for enterprise customers
 * Establishing engineering best practices around testing, deployment and code quality
 * Collaborating directly with product and leadership stakeholders to influence roadmap and delivery priorities