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Leonar · Paris, Île-de-France, France

Lead LLM Engineer

mid_levelfull timePosted yesterday
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Stack mentioned

llmragpythonfastapipostgresqlgcplangchainazureopenai

Licorne Society a été missionné par une startup IA en pleine croissance pour les aider à trouver leur Lead LLM Engineer.

What You Will Own

You will be responsible for one thing:

Make our AI outputs reliable, fast, and indispensable in real workflows.

Concretely

- Design and evolve our LLM / agent architecture

- Own output quality across key use cases (emails, document analysis, etc.)

- Build evaluation systems (datasets, metrics, regression detection)

- Drive fast iteration loops from production data

- Improve retrieval, reasoning, and tool usage

- Ensure production reliability (latency, failure modes, fallback)

- Work directly with product + founders on what to build and why

What This Role Is Really About

Most teams fail because:

- they don’t know what “good output” means

- they don’t have evals

- they iterate randomly

- they overuse agents

Your job is to fix that.

You Will Turn

- vague user problems

- → into structured AI systems

- → with measurable performance

- → that improve every week

What You Need To Be Excellent At

- Shipping real LLM systems

- You’ve built systems used in production (not demos)

- You understand RAG, tools, agents, structured outputs

- You can design full pipelines, not just prompts

- Evaluation-driven development

- You know how to define quality metrics

- You build datasets from real usage

- You run continuous evals to prevent regressions

- Debugging complex failures

- You can trace issues across:

- retrieval

- prompts

- model behavior

- You don’t guess — you isolate and fix

- Speed of iteration

- You move from problem → improvement in hours or days, not weeks

- You use logs, traces, and data — not intuition alone

- Strong judgment

- You know when to:

- use an agent vs a pipeline

- add complexity vs simplify

- You optimize for reliability and user value, not novelty

What We Don’t Care About

- Number of years of experience

- Whether you’ve used a specific framework

- Fancy research credentials

If you can build, debug, and improve real systems, you’re a fit.

What Success Looks Like (first 90 Days)

- Clear eval framework for core use cases

- Measurable improvement in output quality

- Faster iteration cycles across the team

- Reduced hallucinations / failures

- Stronger system architecture decisions

Stack (context, Not Requirements)

- Python (FastAPI)

- Postgres

- Google Cloud

- LangGraph / LangChain (evolving)

- PostHog (product analytics)

- Langfuse (LLM traces)

- LLM APIs (Azure OpenAI)

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