Senior Platform Engineer 200742

Company: Harnham
Apply for the Senior Platform Engineer 200742
Location: London
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

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Posted: October 15th, 2026