Machine Learning Engineer

Oscar; Greater London; On-site; GBP 120,000 - 180,000; Full time

Benefits offered by this job

Central London office

Competitive compensation

Impactful work with financial services

Collaborative environment

Job summary

Oscar is seeking a Senior Software Engineer to design, build and operate LLM-powered workflows for an AI work-execution platform. You will work in Python/FastAPI with LangGraph and LangChain across model providers, focusing on low latency, auditability and cost control.

You will own production RAG pipelines, graph retrieval, and mentor engineers while collaborating with the Executive Committee. Role is based in London’s King’s Cross office with competitive compensation and a strong focus on

Qualifications

• 5+ years of software engineering experience.
• 2+ years running LLM/ML systems in production.
• Hands-on experience with an agent framework (LangGraph/LangChain).
• Production RAG experience with embeddings and vector databases.

Responsibilities

• Build multi-step agentic workflows with tool-calling and human-in-the-loop patterns.
• Integrate models from Anthropic, OpenAI and Bedrock, managing routing and cost.
• Own production RAG pipelines and GraphRAG on Neo4j.
• Measure latency, cost and quality for every model call.
• Apply GDPR-compliant guardrails and ship with FastAPI and PostgreSQL.

Skills

Python

LangGraph

LangChain

LLM systems

RAG pipelines

Education

Bachelor's degree in engineering or computer science

Tools

Neo4j

PostgreSQL

Qdrant

Weaviate

pgvector

Job description

Location: King's Cross, London (in-office) | Experience: 5+ years | Openings: 4

About my client

My client is building an AI work-execution platform for alternative investment firms and their portfolio companies, securely bringing together proprietary data, external sources and workflows to deliver faster, more contextual analysis and better decisions. Backed by a global group of 1,800+ professionals with deep expertise in investment diligence, research, valuation and fund administration, the UK core team is small, senior and high-ownership, with direct access to the Executive Committee.

The role

You will design, build and evaluate the LLM-powered systems at the heart of the platform, working in Python/FastAPI with LangGraph and LangChain across leading model providers. Token cost, latency and auditability are first-class engineering constraints. Senior engineers own major capabilities. Lead engineers also set technical direction and mentor.

Key responsibilities

• Build multi-step agentic workflows (LangGraph / LangChain) with tool-calling, checkpoints and human-in-the-loop patterns
• Integrate Anthropic, OpenAI and Amazon Bedrock models, owning routing, fallback and context and cost management
• Build structured-output systems and MCP tool servers for reasoning over investment documents
• Own production RAG pipelines (Qdrant, reranking, hybrid search) and extend GraphRAG on Neo4j
• Run evaluations (golden datasets, LLM-as-judge, regression gates) and instrument every model call for latency, cost and quality
• Apply responsible-AI guardrails in a UK/GDPR context, shipping on FastAPI, PostgreSQL and AWS with CI/CD
• 5+ years of software engineering with strong Python, including 2+ years running LLM or ML systems in production
• Deep hands-on experience with an agent framework (LangGraph, LangChain or similar) beyond prototypes
• Production RAG experience: embeddings, vector databases, chunking and retrieval evaluation
• Graph-retrieval experience, or the data-modelling fundamentals to pick up Neo4j and Cypher quickly
• Evaluation-led development: you can describe the eval harness of your last system from memory
• Daily use of AI coding tools (Cursor, Claude Code or similar), with a considered view of their strengths and limits

Nice to have:

Qdrant, Weaviate or pgvector in production; MCP servers; LangSmith / LangFuse / Ragas; fine-tuning or open-weight deployment; financial-services documents.

Education:

Bachelor's degree in engineering, computer science or a related field, or equivalent experience.

What's on offer

• Close collaboration with an Executive Committee with 20+ years' experience serving 400+ leading alternative investment clients
• Competitive compensation
• The chance to build something impactful for leading financial services firms
• A supportive, collaborative environment in a central London office