Senior Backend Engineer — Data Platform & AI Agents

Jus Mundi; Paris; Hybrid; EUR 90,000 - 150,000; Full time

Benefits offered by this job

Hybrid work model

5 weeks vacation

Private health insurance

Restaurant vouchers

JM Fest summits

ClassPass membership

Global remote work up to 8 weeks/year

Relocation assistance

Job summary

Jus Mundi is building the AI layer for international law and arbitration and is expanding into new verticals. We seek a Senior Backend Engineer with hands-on AI experience to own the services behind a data platform—agents that acquire documents, the transactional catalog and API, and the processing layer turning raw files into searchable documents.

The role emphasizes backend depth, working with LLMs and agent orchestration as core components, not a modelling or research position.

Qualifications

• 5+ years shipping and operating production backend or data services, with Python, Async I/O, API design, testing discipline, and ownership of services in production.
• Hands-on experience building agent orchestration in production — tool/function calling, memory and state management, error recovery, bounded context, and deterministic contracts around a non-deterministic core.
• Deep data modelling with Postgres, jsonb vs typed columns, indexing, full-text search, and migrations under load.
• Experience with queues/streams, idempotency, at-least-once semantics, atomic writes, and immutable object storage.
• PDF/HTML text extraction, OCR, and multilingual metadata extraction; multilingual corpora is a strong plus.
• DevOps mindset: containers, CI/CD, Kubernetes; you own what you build and operate.

Responsibilities

• Agentic ingestion: build agents that acquire documents from hundreds of sources, orchestration loop, memory, and provably complete operations.
• Backend services and data model: own the transactional catalog and API; design evolving, heterogeneous document schema with provenance and confidence.
• Document processing: extraction, OCR and metadata; ensure versioned, regenerable derived data.
• Quality without manual gates: implement test sets, thresholds, confidence metrics, and regression tracking with Human-In-The-Loop as needed.
• Run what you build: deploy, instrument, and operate services with full traceability of document history.
• Collaborate across squads: design stable interfaces for Search, AI and Product.

Skills

Python

Async IO

API design

Testing

Backend ownership

Agent orchestration

LLM systems

Data modelling

PostgreSQL

JSONB

Full-text search

Idempotency

Atomic writes

Object storage

OCR

Multilingual

Metadata extraction

Kubernetes

CI/CD

Docker

LangChain/LangGraph

OpenSearch/Elasticsearch

LangChain

Tools

PostgreSQL

OpenSearch

Docker

Kubernetes

LangChain

LLM tooling

Job description

About the Role

Jus Mundi is building the AI layer for international law and arbitration — turning a vast, multilingual corpus of case law, treaties, and legal analysis into answers practitioners can trust. We are now expanding beyond arbitration into new legal verticals, and each one potentially adds millions of documents to that corpus.

To support that, we are building a new Data Platform : an autonomous, agent-driven system that discovers, acquires, processes and enriches legal documents end to end, and becomes the company-wide source of truth that Search, AI and Product all consume. It replaces our legacy ingestion paths rather than patching them.

We are looking for a Senior Backend Engineer with hands‑on AI experience to build it with us. You will own the services behind the platform: the agents that acquire documents from hundreds of heterogeneous sources, the transactional catalog and API that everything reads from, and the processing layer that turns raw files into searchable, well‑described documents.

This is a hands‑on senior role with high ownership and real architectural latitude. Backend depth is the core of the role; you should be comfortable working with LLMs and agent orchestration as a first class part of the system, but this is not a modelling or research position.

The Team

You will join the Data team within EPD (Engineering, Product and Design) — a small, senior team made up of an Engineering Manager, a backend/full‑stack engineer, and an AI engineer reinforcing us over the coming months.

We work in close collaboration with the Legal Content team , who own what “correct” means for a legal document, and with the Search, AI and Product squads who consume what the platform produces.

Your mission at Jus Mundi

• Agentic ingestion (core of this role): Build the agents that acquire documents from hundreds of heterogeneous sources — the orchestration loop, tool calling, memory, and the guarantees that make a sweep provably complete rather than approximately complete.
• Backend services and data model (core of this role): Own the transactional catalog and the API in front of it — the single door to the platform’s data. Design a scheme that holds heterogeneous, evolving legal documents with provenance and confidence on every field, and that absorbs new contributors without a migration.
• Document processing: Extraction, OCR and metadata over a messy multilingual corpus.
  Derived data stays versioned and regenerable, so a better model means a re‑run rather than a re‑acquisition.
• Quality without manual gates: We deliberately have no human approval step before a document becomes searchable, so quality has to be measured. Test sets, thresholds, confidence and regression tracking are how a component earns its way into production. We will develop Human‑In‑the‑Loop architecture
• Run what you build: Deploy, instrument and operate your own services. Metrics, logs and traces that let anyone reconstruct a single document’s whole history from one identifier.
• Leverage across squads: Search, AI and Product all build on this platform. You design the stable interfaces they consume, write the RFCs that get decisions validated, and help us grow the team.

Scope will move as the platform does — this is an early‑stage system, and we would rather you help shape the roadmap than inherit it.

Preferred Experience and Skills

• Backend Engineering Depth (critical requirement): 5+ years shipping and operating production backend or data services, with strong Python . Async I/O, API design, testing discipline, and a track record of owning services in production rather than handing them over.
• Agentic & LLM Systems (critical requirement): Hands‑on experience building agent orchestration in production — tool/function calling, memory and state management, error recovery, bounded context, and deterministic contracts wrapped around a non‑deterministic core. Custom architecture or a framework (LangGraph, LangChain, LlamaIndex, or similar) are equally welcome; what matters is that you can point at something you shipped and had to keep working.
• Data Modelling: Postgres in depth — schema design for heterogeneous and evolving data, jsonb versus typed columns, indexing, full‑text search, migrations under load, and a real feel for transactional correctness.
• Systems Judgment: Queues or streams, idempotency, at‑least‑once semantics, atomic writes, object storage treated as immutable truth. You design for retry, reproducibility and graceful degradation rather than assuming the happy path.
• Document & Data Processing: PDF and HTML text extraction, OCR, and structured metadata extraction with LLMs — plus realistic judgement about where quality breaks and what that costs downstream. Multilingual corpora a strong plus.
• Ownership & DevOps Mentality: Containers, CI/CD, Kubernetes or equivalent. You build it, you run it, you own it — including when it pages.
• Senior Behaviours: Turns ambiguity into a plan and a document others can act on; makes explicit trade‑offs rather than reaching for the perfect solution; mentors peers; takes
  accountability for outcomes. Fluent English (our working language, oral and written).

Nice to Have

• Web crawling and scraping at scale — pagination traps, rendering, rate limits, source drift, dedup. We are taking an agentic‑first approach, so this is a real bonus rather than a requirement.
• Legal tech, or another domain where being confidently wrong is expensive.
• Search infrastructure (Elasticsearch / OpenSearch) and multilingual retrieval.
• Enough TypeScript/React to contribute to our internal back‑office UI.
• Experience with the MCP ecosystem, or agent tooling you built yourself.
• Open‑source contributions, or a portfolio of systems you can talk through in depth

Interview process

• Introductory Video Callwith Laurine, Talent Manager (30 min)
• Technical Test at home (1-2 hours) and Remote Debrief Test Session (45 min)
• Live Programming Exercice (1h30)
• Product Interview with an Engineering Manager and a Product manager (45 min)
• Meet the team at the Office + Lunch or Afterwork
• • Immersion with teams (1h30)
  • Culture & Values Interview (45 min)
• Last call with Jean‑Rémi, CEO, or Anna, VP of People (30 min)

Please note that, due to the nature of the sector we operate in, the final steps of our recruitment process include reference calls and a background check.

Need More Reasons to Join Us?

• Enjoy a hybrid working organization that combines remote and on‑site work (2 days).
• Get 5 weeks of vacation each year, and take them whenever it suits you.
• Receive 100% coverage of private health insurance for yourself and your children.
• Enjoy 60% company‑funded restaurant vouchers for your weekday meals (Swile).
• Participate in company‑wide summits called JM Fest to connect and inspire.
• Stay active with a co‑financed ClassPass membership by accessing a variety of fitness and wellness activities.
• Enjoy the flexibility to work from anywhere across the globe for up to 8 weeks per year.
• Receive relocation assistance to help ease your transition to France.
• Last but not least: Experience a commitment to building a warm, inclusive, and diverse environment.

At Jus Mundi, we believe that diversity, equity, and inclusion are key to our success. Confidence can sometimes hold us back from applying for a job, but we’ll let you in on a secret: there’s no such thing as a ‘perfect’ candidate. We celebrate diverse backgrounds, experiences, and identities, and we encourage you to apply regardless of how you identify. Whether you’re early in your career or a seasoned professional, your unique perspective and skills are what matter most. Join us in building a workplace where everyone feels valued, empowered, and excited to contribute their best work every day.