Senior RAG Engineer - LangChain/Production AI Systems

Wallester; City Of London; On-site; GBP 60,000 - 90,000; Full time

Job summary

A leading financial technology company in the City of London is seeking an exceptional engineer to develop an intelligent knowledge base using RAG systems. The ideal candidate will have extensive experience with LangChain and n8n, strong skills in Python, and a track record of production-level AI/ML projects. This opportunity offers competitive benefits and a dynamic work environment.

Benefits

30 days holiday

Private Medical cover

Pension scheme

Quarterly Team-Buildings

Corporate events

Work Anniversary Celebrations

Affiliate program

Referral program

Qualifications

• Expertise in designing and implementing RAG architectures.
• Minimum 3-5 years experience in software development.
• Proven experience with n8n and LangChain in production.

Responsibilities

• Design and implement a RAG system for knowledge base.
• Integrate various department systems using n8n.
• Optimize system performance and caching.

Skills

LangChain/LangGraph expertise

Software development (AI/ML)

Python programming

n8n production workflows

Tools

LangChain

n8n

Google Drive

pgvector

Pipedrive

LangSmith

LangFuse

Job description

About us

Wallester is a cutting-edge financial technology company that specializes in providing innovative solutions for businesses seeking to modernize their payment systems. By offering white-label card issuance platforms, seamless integration with existing infrastructure, and comprehensive support for both digital and physical cards, Wallester empowers companies to enhance their financial services and customer experience. Recognized as a leader in the FinTech space, Wallester has earned a reputation for its state-of-the-art technology, security, and scalability. Whether you are a startup or an established enterprise, Wallester delivers flexible, reliable solutions tailored to meet the evolving needs of the digital economy.

About the role

We're seeking an exceptional engineer specialized in RAG (Retrieval-Augmented Generation) systems to build Wallester's intelligent knowledge base. You'll be responsible for the architecture, development, and deployment of a RAG system capable of ingesting hundreds of documents (Drive, emails, history) and providing perfect institutional memory accessible in natural language.

Progressive deployment over 9 months: General knowledge base → Department integrations (Sales, Finance, Support) → Advanced features and scaling.

We're looking for a true expert capable of designing and implementing complex RAG architectures with LangChain/LangGraph and orchestrating workflows with n8n.

What you'll do

General Knowledge Base

• Design complete RAG architecture with LangChain
• Implement Google Drive ingestion pipeline (5000+ documents)
• Build 3-way hybrid search (semantic + BM25 + pattern matching)
• Deploy Supabase with pgvector optimization
• Create LangGraph workflows for orchestration

Department Integrations

• Connect Pipedrive (Sales), Admin Panel (Finance), Support systems
• Develop autonomous agents per department with LangGraph
• Build n8n workflows for business logic
• Implement conversation memory and query routing

Production & Scaling

• Optimize for 1000+ queries/day with <1s latency
• Implement intelligent caching and error handling
• Set up RAG evaluation metrics (precision, recall, faithfulness)
• Monitor with LangSmith/LangFuse

What you'll need

• Truly masters LangChain/LangGraph in production
• Has built production RAG systems (not just POCs)
• Understands trade-offs (latency, quality, cost, chunking)
• Knows the LangChain ecosystem (LangSmith, LangFuse, integrations)
• Experience 3-5 years minimum in software development with production AI/ML projects
• Python expert with complex production projects
• LangChain/LangGraph: Confirmed production experience (required)
• n8n: Production workflow experience with complex pipelines (required)
• RAG/LLM portfolio: Deployed systems, GitHub, technical articles
• Bonus: TypeScript, Redis, advanced n8n scaling (workers, queues)

We offer

• 30 days holiday (pro rata), plus UK Bank and Public Holidays
• Private Medical cover, including Family if applicable (after Probation Period)
• Pension scheme (after 3 months)
• Quarterly Team-Buildings
• Corporate events: regular employee gatherings (Summer Days, Winter Gala)
• Work Anniversary Celebrations
• Affiliate program for employees
• Referral program for employees