Principal Engineer - Freelance (M/F)

Daily Rate (TJM): 750

Reporting directly to the Head of Engineering (Olivier Hervieu), you will be the technical conductor of the future digital platform.

You combine strong expertise in software architecture with a concrete ability to manage the integration of complex third-party systems and to keep your hands in the code (individual contribution, PR reviews).

RESPONSIBILITIES & DAILY ROLE

Architecture & System Vision:

• Design and guarantee the integrity of the target IS architecture in partnership with the Head of Engineering.
• Define distribution APIs, inter-application communication, and data dissemination.

Systems & Partner Integration:

• Lead and scope complex integrations with our external partners and SaaS (inventory, PSP, railway systems/SNCF Réseau).
• Be proactive and a driving force when dealing with technical partners to advance integrations without getting blocked by documentation or dependencies.

Development & Technical Excellence:

• Develop core components and APIs of the backend platform.
• Implement and maintain engineering best practices (code/PR reviews, documentation, software quality).
• Ensure technical cohesion as teams (internal and service providers) grow.

Interface & Collaborations:

• Collaborate with Front teams (React/Native) for API exposure and design.
• Exchange with providers in charge of the Cloud/AWS Landing Zone.

TECHNOLOGICAL STACK & ENVIRONMENT

• Backend / Language: Python (preferably) or TypeScript/JS. (Note: Go, Java, or C# are explicitly excluded for the main core).
• Cloud & Infra: AWS, containerization (Kubernetes).
• Frontend / Mobile (for API interface): React, native mobile apps.
• Tooling & Culture: Daily use of AI tools (Claude, ChatGPT) is encouraged to optimize productivity.

REQUIRED PROFILE

EXPERIENCE & REQUIRED SKILLS:

• Experience: Senior / Lead Engineer / Principal Engineer (minimum 7 years of experience) with a proven track record in designing distributed systems and API/Microservices architectures.
• Background: Successful experience in complex and high-stakes IS integrations (high-traffic e-commerce, transport, e-travel, critical SaaS). Past experience within large engineering programs or a Lead / ex-CTO role wishing to "step back" into technical hands-on work is a real plus.
• Integration Capacity & Proactivity: Natural leadership, tenacity, and interpersonal ease to interact with partners/vendors from varied cultures.
• Languages: Basic technical English (commits, documentation, messages).