Lead Engineer - Node.js, React Native, AI Agents

Lead Engineer | Node.js, React Native, AI Agents

Location: London / hybrid preferred, or remote from Central & Eastern Europe
Level: Mid-to-Senior, hands-on Lead
Employment: Full-time, permanent

About the company

We are an early-stage UK product company building an AI-powered platform focused on professional relationships and network intelligence.

The product combines a social graph, relationship data and an AI agent that helps users identify relevant people, understand their network and strengthen important connections.

We are looking for a Lead Engineer / Founding Senior Engineer who will own the technical architecture, write production code and help grow the engineering team.

This is a hands-on engineering role, not a pure management position.

Tech stack

• Node.js / TypeScript / Express
• React Native + Expo
• MongoDB Atlas
• Atlas Vector Search + BM25 / hybrid retrieval
• OpenAI / custom LLM tool-calling agents
• AWS EC2, Cognito, S3
• Docker, Nginx
• GitHub Actions / CI/CD

Responsibilities

• Own technical architecture and production infrastructure
• Ship features across backend, mobile and AI agent layers
• Build and improve LLM agents, prompts, tool-calling flows and evaluation
• Mentor engineers and establish strong engineering practices
• Implement privacy-by-design and GDPR requirements
• Build and use synthetic data for development, testing and model evaluation
• Own CI/CD, monitoring, secrets management and incident response
• Own application and infrastructure security
• Secure AI agents against prompt injection, data leakage and unintended tool actions
• Work directly with the Founder on product and architecture decisions

Must-have

• 4+ years of professional software engineering experience
• Strong Node.js / TypeScript backend experience
• Experience owning real production systems
• Comfortable across backend, frontend/mobile and infrastructure
• MongoDB or similar document database experience
• Hands-on experience building LLM agents and prompting systems
• Experience with agent tool usage and evaluation
• Practical GDPR and data privacy knowledge
• Strong security fundamentals
• Understanding of AI-agent risks such as prompt injection, data leakage and unintended actions
• Experience working with synthetic data
• Production deployment, monitoring and incident-response experience
• Previous mentoring or technical leadership experience
• Comfortable with ambiguity and a fast-moving startup environment

Nice-to-have

• React Native / Expo
• RAG / vector search
• AWS Cognito
• Previous Tech Lead, CTO or founding engineer experience
• Application security / pentesting background
• Experience securing LLM / AI-agent applications

Compensation

Competitive salary + equity depending on experience and location.

We are looking for someone interested in a long-term role and growing together with the company, not a freelance or short-term contract position.