Full-stack Software Engineer (Contract)

Who we are
Lemrock builds the infrastructure of agentic commerce.
Tomorrow, consumers won't just buy on e-commerce websites. They will discover, compare and purchase directly inside conversational AI interfaces like ChatGPT, Perplexity, and a growing long tail of specialized AI assistants.
For brands, this is a major shift: if they are not present in these environments, they become invisible.
Our mission: enable any brand to exist, sell and distribute in this new channel.
We raised a €7M seed round (the first in Europe on this market), with Jean-Baptiste Rudelle, founder of Criteo, on our board, and the Bpifrance DeepTech label.
Today, Lemrock is already:

• 100M+ conversations per month
• 150+ brand clients
• a $100B market structuring at high speed

Context
You'll join a small, high-ownership engineering team building production systems that serve millions of users. We care deeply about code quality and clean architecture, and we intend to keep it that way as we scale.
As our freelance Full-stack Software Engineer, full-time, you will work inside the team like any of its engineers: same codebase, same standards, same ownership.
Your mission
Your goal is to build and ship the product that powers Lemrock's commerce infrastructure, with full ownership, from design to production. Concretely, you will:

• Ship features end-to-end that reach millions of users, from data model and API design to the interface they interact with.
• Scale and harden our backend as traffic, integrations, and product complexity grow.
• Shape the architecture of the codebase: enforce clean boundaries, maintain modularity, and make decisions that compound as the team scales.
• Move fast across the stack (backend, frontend, infra, data), wherever the highest-impact work is on any given week.

From day one

• You push your first code to production within your first days, then ship every week
• You write excellent, well-tested code the team can build on
• You are reliable: when you take something on, it gets delivered

Candidate profile

• Strong academic background, proven professional track record, or hands-on entrepreneurial experience
• 3+ years of hands-on software engineering experience
• Deep proficiency in TypeScript
• Experience with structured backend architectures (DDD, hexagonal, or similar)
• Has owned features end-to-end: data model → API → frontend → deployment
• Uses AI coding tools every day (Cursor, Claude Code)
• Thrives in ambiguity and 0-to-1 environments: ex-founders or entrepreneurial mindsets are a strong fit
• Professional proficiency in French & English

Tech stack
Core (required)

• TypeScript, NestJS, React
• PostgreSQL, Redis
• Docker
• Clean architecture patterns (hexagonal, ports & adapters)

Bonus (appreciated but not required)

• GCP (Cloud Run, Pub/Sub, BigQuery), Terraform
• Vector databases, embeddings, LLM integrations
• Domain-Driven Design (DDD), CQRS
• TanStack (Router, Query, Table), shadcn/ui, Tailwind, Vite
• Durable workflows (Inngest, Temporal)

The mission

• Freelance, full-time, starting ASAP
• 3 months minimum, extended to 6 or 12 months when it works well
• For the right person, the mission can turn into a permanent role

Why join us

• Join a company in early breakout mode, already generating revenue, with a clear technological edge and strong financial backing to fuel its growth
• Work directly with an experienced team: two repeat YC founders who've scaled product & tech before, a former strategy/innovation director (10 years in the sector), and ex-strategy consultants (McKinsey QuantumBlack, BCG)
• Be part of the next structural shift of the web: agentic interfaces
• Own mission-critical topics, grow fast, and shape the company's future trajectory

Daily rate discussed during the process.