Senior Backend Engineer - Scale Real-Time Systems

Leonar; Paris; On-site; EUR 70,000 - 110,000; Full time

Job summary

Leonar is seeking a Senior Backend Developer based in Paris or Bordeaux to join the Tech team. You will work closely with the Head of Software to scale systems and accelerate product development, taking ownership of architecture and delivering high-impact features.

You'll be part of a small, agile team shipping daily to production, with tens of thousands of trips per day and real-time messaging between services and IoT devices.

Qualifications

• Experience: 5+ years in software development, ideally in R&D environments or product-driven tech teams.
• Tech stack: Python; familiarity with Node.js or Go is a plus.
• Problem-solving mindset with pragmatism and scalable solutions.
• Ownership and impact: take responsibility for your work and its impact on users and the product.
• Clear communication, written and verbal, with ability to adapt messaging to technical or non-technical audiences.
• High standards for code, architecture, and how components fit together.

Responsibilities

• Feature development: Build new product features and contribute to the technical roadmap, designing solutions that balance user needs with strong technical foundations.
• Infrastructure maintenance & improvement: Maintain existing systems, troubleshoot incidents, and continuously improve backend services.
• Performance optimisation: Reduce recurring incidents, improve capacity planning, and optimise backend architecture to ensure scalability and reliability.
• Complex problem-solving: Take ownership of deep technical challenges to ensure the robustness and quality of our platform.

Skills

Python

Node.js

Go

Ownership

Communication

Job description

Leonar is seeking a Senior Backend Developer based in Paris or Bordeaux to join the Tech team. You will work closely with the Head of Software to scale systems and accelerate product development, taking ownership of architecture and delivering high-impact features.

You'll be part of a small, agile team shipping daily to production, with tens of thousands of trips per day and real-time messaging between services and IoT devices.