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LesJeudis

Fullstack Developer (Part-time)

LesJeudis
France · Temporary · Mid-Senior
Chainlabs is a cutting-edge Web3 data analytics and software start-up specializing in uncovering illicit activities on the blockchain. As the largest broker of labeled wallet datasets to leading Web3 AML and KYT companies, our clients include Chainalysis, TRM Labs, Coinbase Research, Elliptic, and Crystal Blockchain. Our mission is to create actionable intelligence and safeguard the cryptocurrency ecosystem.

Role Overview

Role

We are seeking a versatile and self-driven Fullstack Backend Engineer who thrives in a rapid-prototyping environment to join our fully remote team. You'll play a key role in building two forward-looking products:

  • A crypto asset recovery platform to simplify blockchain forensics for everyday users.
  • A suite of AI-integrated communication tools, including:
    • An AI-powered Slack Company Coach combining Slack API, Zapier automations, and custom dashboards.
    • A WhatsApp-based messaging assistant for landlords and tenants, powered by large language models and local service data.
This is a unique opportunity to shape early-stage products that fuse blockchain intelligence, LLMs, and automation into real-world applications.

This role will initially be part-time, with the potential to transition into a full-time position after a few months based on performance and project needs. We offer competitive compensation, paid in fiat or cryptocurrency.

Requirements

  • Proficiency in JavaScript/TypeScript, with hands-on experience in React.js or Vue.js.
  • Backend experience with Node.js + Express, Firebase, or Supabase.
  • Experience integrating Slack API and Twilio/WhatsApp Business API.
  • Proven ability to work with LLMs (OpenAI, Claude, Mistral, etc.) in production environments.
  • Understanding of prompt engineering, context window strategies, and vector memory (e.g., Pinecone, ChromaDB).
  • Experience with AI pair programming tools such as Cursor AI, GitHub Copilot, or Cody (non-negotiable).
  • Comfortable embedding dashboards using tools like Streamlit, Superset, or Metabase.
  • Experience working with PostgreSQL or similar relational databases.
  • Knowledge of blockchain data, wallet structures, and APIs like Bitquery, Etherscan, or Covalent.
  • Strong grasp of Git, version control, and modern dev workflows.
  • Experience with analytics tools such as Hotjar, Google Analytics, or Mixpanel.

Nice to Haves:

  • Experience building with chatbot frameworks like LangChain, Dialogflow, or custom GPT tools.
  • Familiarity with A/B testing platforms such as Google Optimize or Optimizely.
  • Previous work on fintech or crypto products.
  • Exposure to frontend/backend deployment tools such as Netlify, Vercel, Heroku, or GCP.
  • Comfort working in fast-paced, iterative, early-stage environments with limited structure.

Key Responsibilities

  • Rapidly prototype and iterate on user-facing features and backend infrastructure.
  • Build custom integrations with Slack and WhatsApp, enabling AI-assisted communication flows.
  • Integrate LLMs into user workflows to provide automated responses and dynamic data retrieval.
  • Develop dashboards and internal tools to visualize behavior across messaging platforms and blockchain data.
  • Create blockchain forensic tools with interactive visualizations (2-3 hop tracking with tooltips).
  • Manage authentication, access control, analytics, and testing frameworks across all products.
  • Ship clean, maintainable code and help us scale from MVP to production with security and performance in mind.

Benefits

  • Flexible, remote-first role with full-time or part-time options.
  • Competitive compensation, paid in fiat or cryptocurrency.
  • Work directly with a data scientist founder and a fast-moving product team.
  • Opportunity to shape the core of AI + blockchain products with real impact.
  • Exposure to leading tools and the latest AI development workflows.
  • Fast, transparent, and curiosity-driven company culture.
  • Potential for long-term or expanded responsibilities based on performance.

Key Skills

Ranked by relevance

blockchain ai slack cryptocurrency google analytics prototyping postgresql streamlit firebase mixpanel reactjs heroku hotjar git gcp
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Country Guide

France

Large economy with strong startup and AI ecosystem

Posted
Jun 24, 2025
Type
Temporary
Level
Mid-Senior
Location
Paris
Company
LesJeudis

Industries

IT Services IT Consulting

Categories

Engineering Information Technology

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