Senior Platform Engineer 200742

Harnham; Greater London; On-site; GBP 90,000 - 130,000; Full time

Benefits offered by this job

Direct exposure to founders & senior领导

Clear progression as the team grows

Early-stage influence on engineering方向

Job summary

Harnham is seeking one of its first senior engineering hires to help shape an AI-driven platform for enterprise clients. You will own core product development, work with founders to set technical direction, and scale AI-powered solutions from early concept to production.

You will build features across the full stack, optimise LLM-enabled apps, and design scalable APIs while aligning with business goals and customer needs.

Qualifications

• Proven experience as Product Engineer or Software Engineer with delivered LLM-powered products.
• Strong backend skills with Node.js and TypeScript in production environments.
• Experience designing APIs and distributed systems, with exposure to frontend tech a plus.

Responsibilities

• Build and ship product features across the full stack.
• Develop and optimise LLM-enabled applications for enterprise users.
• Own retrieval augmented generation pipelines and AI integrations.
• Design scalable API-first products and backend services.
• Improve model performance, reliability, evaluation frameworks and guardrails.
• Manage token usage, response quality and cost strategies.
• Contribute to cloud infrastructure and deployment in AWS.
• Establish engineering best practices across testing, delivery and software quality.
• Collaborate with stakeholders to shape product directions and priorities.

Skills

Product Engineer

Software Engineer

LLM-powered products

Backend engineering

Node.js

TypeScript

APIs & distributed systems

AWS

Startup/high-growth experience

Communication & autonomy

React frontend exposure

Tools

AWS

Job description

This is an opportunity to join an early-stage AI business at a pivotal point in its growth. As one of the first senior engineering hires, you will play a key role in shaping the product, influencing technical direction, and building scalable AI-powered solutions for enterprise customers.

The Company

They are a venture-backed AI startup building advanced software that helps organisations better understand customer behaviour and make more informed business decisions. Having secured significant early-stage funding and already engaging with enterprise customers, they are moving from proof-of-concept work into wider commercial growth. The team combines expertise across product, engineering and research, with a strong focus on delivering real-world impact through AI.

The Role

You will take ownership of core product development, working closely with senior leadership to build and scale an AI-driven platform.

Responsibilities include:

• Building and shipping product features across the full stack
• Developing and optimising LLM-enabled applications for enterprise users
• Owning retrieval augmented generation pipelines and AI integrations
• Designing scalable API-first products and backend services
• Improving model performance, reliability, evaluation frameworks and guardrails
• Managing token usage, response quality and cost optimisation strategies
• Contributing to cloud infrastructure and deployment processes within AWS
• Establishing engineering best practices across testing, delivery and software quality
• Working closely with stakeholders to shape product direction and priorities

Your Skills & Experience

• Strong commercial experience as a Product Engineer or Software Engineer
• Experience building and scaling LLM-powered products in production environments
• Strong backend engineering skills, ideally with Node.js and TypeScript
• Experience designing APIs and distributed systems
• Knowledge of cloud platforms, ideally AWS
• Comfortable working across both product and technical decision-making
• Experience in startup or high-growth environments where ownership is expected
• Strong communication skills and the ability to work autonomously
• Exposure to React or modern frontend technologies is beneficial
• Experience within regulated industries, including Financial Services, is advantageous but not essential

What They Offer

• Opportunity to influence engineering strategy from an early stage
• Direct exposure to founders and senior leadership
• Significant scope for progression as the team scales