Senior Python AI Engineer

WTW; Greater London; Hybrid; GBP 90,000 - 140,000; Full time

Benefits offered by this job

Hybrid work options

Private healthcare

Life insurance

Pension with matched contributions up

Volunteer day

Share scheme

Electric vehicle car scheme

Job summary

WTW is seeking a Senior Python AI Engineer in the London area to design and build AI-enabled enterprise services. You will craft AI-powered backends, orchestration workflows, and scalable APIs using FastAPI, LangGraph and LangChain, delivering robust RAG pipelines and reliable production systems.

You’ll collaborate with architects and product owners, contribute to testing, observability and performance improvements, and explore cutting-edge AI tech for enterprise use.

Qualifications

• Strong Python development experience in production applications.
• Experience building APIs and backend services, ideally with FastAPI.
• Proven experience building applications with LLMs, using LangChain and/or LangGraph and agentic workflows.
• Experience developing RAG solutions and integrating multiple systems and data sources via REST APIs.
• Solid engineering practices — automated testing, source control, code review and CI/CD — with a focus on production-quality software over prototypes.
• A good understanding of production generative AI challenges: retrieval quality, grounding, context management, evaluation, reliability and performance.

Responsibilities

• Design, develop and maintain AI-powered application services using Python.
• Build and evolve agentic workflows and AI orchestration using LangGraph and LangChain.
• Develop scalable APIs and backend services using FastAPI.
• Design and implement Retrieval-Augmented Generation (RAG) pipelines that combine LLMs with enterprise knowledge and data sources.
• Work on retrieval strategies including vector, metadata and graph-based retrieval.
• Collaborate with architects, developers, product owners and other technical specialists to turn requirements into robust technical solutions.
• Participate in technical design discussions, code reviews and engineering decision-making.

Skills

Python

APIs

FastAPI

LangChain

LangGraph

LLMs

RAG

Azure

Docker

Kubernetes

CI/CD

Tools

LangGraph

LangChain

Azure AI

Cosmos DB

Job description

Ready to build production AI that actually ships — not another proof-of-concept chatbot?

Join us as a Senior Python AI Engineer on HR Expert, where you'll help design and build a modern, AI-enabled application from the inside out. This is a genuinely hands-on engineering role at the cutting edge of generative AI, agentic systems and Retrieval-Augmented Generation (RAG) — solving the hard, interesting problems around AI orchestration, information retrieval and grounding that most engineers only get to read about.

With strong Python at the heart of everything you do, you'll work across a modern AI stack — LangGraph, LangChain, FastAPI, Azure, vector search and graph databases — building sophisticated, reliable systems that scale. You'll join a talented, multidisciplinary team that values engineering craft as much as innovation, and any wider full-stack or .NET background you bring will be a real bonus. If you've already built LLM-based applications and you're itching to take them to the next level of sophistication, reliability and scale, this is your chance to shape how AI is genuinely used in enterprise software.

Beyond the tech, we're looking for someone who enjoys solving challenging problems, can take them from design through to production, communicates clearly with technical and non-technical stakeholders, and takes ownership of the quality and reliability of their work.

Come and help us define what great enterprise AI looks like.

The Role

• Design, develop and maintain AI-powered application services using Python.
• Build and evolve agentic workflows and AI orchestration using LangGraph and LangChain.
• Develop scalable APIs and backend services using FastAPI.
• Design and implement Retrieval-Augmented Generation (RAG) pipelines that combine LLMs with enterprise knowledge and data sources.
• Work on retrieval strategies including vector, metadata and graph-based retrieval.
• Contribute to the architecture and implementation of complex AI workflows involving multiple agents, tools and data sources.
• Integrate AI services with the wider HR Expert application and existing enterprise systems.
• Develop and deploy solutions using Microsoft Azure, working across relational, document, vector and graph-based data stores.
• Collaborate with architects, developers, product owners and other technical specialists to turn requirements into robust technical solutions.
• Participate in technical design discussions, code reviews and engineering decision-making.
• Help establish good engineering practices around testing, observability, performance and maintainability of AI applications.
• Investigate emerging AI technologies and evaluate where they can provide practical value to the product.
• Occasionally contribute to frontend or existing .NET services where needed — though this is not the primary focus of the role.

What you'll bring

• Strong Python development experience in production applications.
• Experience building APIs and backend services, ideally with FastAPI.
• Proven experience building applications with LLMs, using LangChain and/or LangGraph and agentic workflows.
• Experience developing RAG solutions and integrating multiple systems and data sources via REST APIs.
• Solid engineering practices — automated testing, source control, code review and CI/CD — with a focus on production-quality software over prototypes.
• A good understanding of production generative AI challenges: retrieval quality, grounding, context management, evaluation, reliability and performance.
• Experience in any of the following would be particularly valuable: complex RAG architectures (multi-stage retrieval, hybrid search, reranking, agent-driven retrieval); graph databases and GraphRAG, particularly ArangoDB; Azure AI services (Azure OpenAI, AI Search, Cosmos DB, AKS, Functions); vector/semantic search; Docker and Kubernetes; multi-tenant applications; LLM evaluation and observability; and Angular, NgRx or .NET / C# development.

What we offer

Enjoy a benefits package designed to help you thrive, both professionally and personally. You'll receive 25 days of annual leave plus an extra WTW day to relax and recharge. Our comprehensive health and wellbeing offering includes private healthcare, life insurance, group income protection, and regular health assessments, all giving you peace of mind. Secure your future with our defined contribution pension scheme, featuring matched contributions up to 10% from the company.

We support your growth and balance with hybrid working options, access to an employee assistance programme, and a fully paid volunteer day to make a difference in your community. On top of these, you can opt into a variety of additional perks including an electric vehicle car scheme, share scheme, cycle-to-work programme, dental and optical cover, critical illness protection, and much more. Start making the most of your career and wellbeing with a range of benefits tailored for you.

Equal Opportunity Employer

We’re committed to equal employment opportunity and provide application, interview and workplace adjustments and accommodations to all applicants. If you foresee any barriers, from the application process through to joining WTW, please email [e-mail]