Full Stack AI Engineer-Belfast

Job description

With a legacy as a pioneer in the ALSP market, Factor leads the next evolution in legal services through AI-integrated contracting. Factor is the market leader in Integrated Law™, combining the expertise of Traditional Law, the efficiency of New Law, and the close business integration of In-house legal to deliver complex legal work at scale. Factor works alongside corporate legal departments to solve for the ever-increasing demands and complexity of transactional legal work. Our "do while transforming, transform while doing" approach combines specialist expertise, AI-powered solutions, and business process knowledge to deliver better performance, better business and legal outcomes, and a transformed contracting experience. Our clients span Fortune 500 companies including global banks, major pharmaceutical companies and large technology firms. We believe that the more diverse our team becomes — in backgrounds, skills, experiences, and perspectives — the higher our creative potential as a company. We are dedicated to growing a diverse, inclusive company where individuals of all backgrounds thrive. We are comprised of more than 300 lawyers, legal specialists, technologists, and process consultants across Europe and North America – Join us! **The Role:** Factor Law is hiring a Full Stack AI Engineer based in Belfast to build production-grade AI products for complex legal workflows. This is a hands-on engineering role for someone who can move confidently from backend architecture to frontend delivery, from document ingestion to user experience, and from prototype to production without waiting for detailed step-by-step instructions. You will join a high-autonomy product and engineering environment building AI-powered tools that help legal teams work faster, more accurately and with more confidence. The work will sit at the intersection of contract intelligence, document processing, retrieval, AI orchestration, workflow automation, enterprise authentication, asynchronous job handling and complex user interfaces. This role is for a builder. We are looking for someone who can use AI-assisted coding tools aggressively and responsibly, particularly Codex, while still owning correctness, security, maintainability and production quality. The right person will use AI to move faster, not to cut corners. ### Responsibilities - - Build production services using Python, FastAPI and Pydantic models. - Develop APIs and backend workflows that support AI-enabled document and contract intelligence. - Work with PostgreSQL, SQLAlchemy and Alembic to model, migrate and operate reliable data layers. - Build and maintain asynchronous job systems, including queue processing, retries, idempotency, dead-letter handling, cancellation, progress tracking and failure recovery. - Use Redis for caching, transient state, job status and coordination, with sensible reliability patterns such as timeouts, circuit breakers and graceful degradation. - Build React and TypeScript interfaces that consume backend services cleanly and provide users with transparent job states, useful error handling and polished interaction patterns. - Use TanStack Query for server state, including query key factories, cache invalidation, optimistic updates and polling patterns for long-running AI jobs. - Support document-heavy workflows, including ingestion, retrieval, structured extraction, redlining, rich text editing and AI-assisted review. - Build features that respect enterprise security expectations, including authentication, authorisation, secure data handling and auditability. - Operate within Azure-based environments, including services such as Blob Storage, Key Vault, managed databases, Redis and containerised deployments. - Instrument production systems using Application Insights or equivalent observability tooling. - Use AI coding tools to accelerate implementation, debugging, refactoring, testing and documentation, while maintaining high code quality. - Improve developer experience by reducing boilerplate, improving test coverage, simplifying local setup and documenting repeatable patterns. - Move fluidly between infrastructure and product delivery when needed. ### Essential Criteria - - Minimum 3-5+ years of professional software engineering experience, or equivalent evidence of exceptional delivery. - Strong production experience with Python and FastAPI. - Strong working knowledge of Pydantic, PostgreSQL, SQLAlchemy and Alembic. - Experience building React and TypeScript applications that consume real backend services. - Demonstrable experience shipping production software, not only prototypes or internal scripts. - Comfort working with asynchronous jobs, background workers or queue-based systems. - Experience using Redis for caching, job status, state or coordination. - Practical experience with Docker and cloud-hosted deployments. - Strong ability to debug across backend, frontend, database, authentication and infrastructure layers. - High fluency with AI-assisted coding tools such as Codex, Cursor, Claude Code or similar. - Ability to work with ambiguity and make progress without waiting for perfect specifications. - Clear ownership mentality, including follow-through on edge cases, tests, production behaviour and user impact. - Legally eligible to work in the relevant location. ### Desirable Criteria - - Experience with Azure services, especially Blob Storage, Key Vault, managed PostgreSQL, managed Redis and containerised application hosting. - Experience with enterprise authentication, especially Azure MSAL, OAuth/OIDC, token refresh, redirects and test-time auth bypasses. - Experience with RAG, embeddings, vector search, document chunking, retrieval evaluation or LLM orchestration. - Experience building lega