Ai Engineer - Freelance - Freelance

Collective.Work; England; Hybrid; GBP 90,000 - 130,000; Full time

Job summary

Collective.work in London, UK, is hiring an AI-powered software engineer to design, develop, and ship AI features across the recruitment platform. You will work across the AI and JavaScript stacks, building backend services, data pipelines, APIs, and user-facing features to improve search, matching, and outreach.

The role requires strong AI engineering experience, full-stack JS skills, and a product-minded, autonomous individual who thrives on experimentation and rapid iteration in a hybrid work

Qualifications

• Strong engineering fundamentals.
• AI engineering experience with LLMs or ML systems.
• Full-stack JavaScript skills with backend/API focus.
• Product-minded approach balancing quality, speed and impact.
• Experimental mindset with rapid hypothesis testing.
• Ownership and autonomy in fast-moving teams.
• Curiosity about AI and translating capabilities into product features.
• Experience with semantic search, embeddings, vector databases, information retrieval, ranking systems, or model evaluation.

Responsibilities

• Build AI features across sourcing, matching, outreach, distribution, and ATS integrations.
• Improve AI models via experimentation, evaluation, prompts, and optimization.
• Leverage large-scale profile data to enhance search, ranking, and recommendations.
• Integrate LLMs and AI tech into scalable, low-latency product experiences.
• Experiment with new models and tools and turn ideas into features.
• Own the full stack across AI and JavaScript, including backend services, data pipelines, and APIs.
• Define and track quality metrics and use feedback to improve AI systems.

Skills

Engineering fundamentals

AI engineering

Full-stack JavaScript

Product mindset

Experimental mindset

Ownership

Curiosity about AI

Semantic search

Embeddings

Tools

LLM APIs

APIs

Job description

Job description

Context

Collective is building the next generation of AI-powered recruitment technology. Their mission is to help professional recruiters find, engage, and hire the right talent faster. Currently, they support over 20,000 recruiters and headhunters across France, Belgium, Spain, and the wider EMEA market, and are accelerating their expansion into the UK.

The platform integrates a suite of AI agents covering the entire sourcing workflow, from candidate discovery and job posting to personalised outreach and ATS integrations. Their technology combines a database of 800M+ public professional profiles with an embedded network of 1M+ active candidates, providing a strong foundation for smarter talent discovery.

Missions

• Build new AI features by designing, developing, and shipping AI-powered capabilities across the suite of agents, including sourcing, candidate matching, outreach, job distribution, and ATS integrations.

• Improve AI models continuously through experimentation, evaluation, prompt engineering, and model optimisation to enhance quality, relevance, and reliability.

• Leverage large-scale professional profile data and active candidate networks to improve search, ranking, matching, and candidate recommendations.

• Build production-grade AI systems by integrating LLMs and other AI technologies into scalable, reliable, and low-latency product experiences.

• Experiment with new models, tools, and techniques, evaluate their real-world impact, and quickly turn promising ideas into features.

• Own the full stack, working across AI and JavaScript stacks, including backend services, data pipelines, APIs, and user-facing product features.

• Define and track quality metrics, build evaluation workflows, and use product feedback and real-world usage to continuously improve AI systems.

Tools & Environment

• AI & LLMs: LLM APIs, prompting, tool use, AI agents, evaluation, and model optimisation.

• Development: JavaScript / TypeScript, backend services, APIs, and full-stack product development.

• Search & data: Large-scale profile data, embeddings, semantic search, candidate ranking, and matching.

• Production AI: Reliability, latency, observability, experimentation, and continuous improvement.

Working Conditions

• Location: London, UK (Hybrid work model)

• Company: Collective.work

• Sector: AI-powered recruitment technology

• Expansion phase: Accelerating growth into the UK market

• User base: 20,000+ recruiters across multiple European markets

Requirements

1. Strong engineering fundamentals: ability to build clean, maintainable, production-ready software and take ownership from idea to deployment
2. AI engineering experience: built applications using LLMs, AI APIs, or machine learning systems and understand production reliability
3. Full-stack JavaScript skills: comfortable with JavaScript/TypeScript and modern JS ecosystem, especially backend and API development
4. Product mindset: focus on solving real user problems balancing technical quality with speed and impact
5. Experimental mindset: enjoy testing hypotheses, evaluating results, and iterating quickly
6. Ownership and autonomy: comfortable operating in a fast-moving environment, making technical decisions, and driving projects forward
7. Curiosity about AI: actively follow AI developments and translate new capabilities into practical applications
8. Experience with semantic search, embeddings, vector databases, information retrieval, ranking systems, RAG, agentic workflows, or model evaluation is a strong plus
9. Willingness to learn a new domain (recruitment) and build impactful products