Mid-Level Backend Python Developer — Freelance (FR or ESP) - Freelance

Mission Context

We are supporting a fast-growing French scale-up operating several SaaS products and an international B2B marketplace.

As the company accelerates its product development and continues to scale its technical platform, the engineering team is looking for a confirmed Backend Python Developer to strengthen its backend capabilities.

The consultant will work on topics related to backend development, API reliability, application performance, data flows and the progressive evolution of the existing architecture.

This role is particularly suited to a hands-on developer who has already worked in a startup or scale-up environment and is comfortable contributing within a fast-moving, product-oriented organisation.

Mission Objectives

The consultant will contribute to the design, development and optimisation of Python backend services supporting a high-usage SaaS platform.

They will participate in the progressive modernisation of the architecture, the improvement of application performance and reliability, and the industrialisation of development and deployment practices.

The consultant will work closely with more senior engineers and contribute directly to delivering robust and scalable product features.

Main Responsibilities

• Design, develop and maintain backend services in Python using frameworks such as FastAPI, Django or Flask.

• Build and improve secure, reliable and performant REST and GraphQL APIs.

• Contribute to the progressive evolution of the platform towards a more modular and scalable architecture.

• Identify and resolve backend performance issues related to API latency, database queries, traffic management and application reliability.

• Participate in the development and maintenance of distributed and asynchronous workflows.

• Contribute to data consistency, transaction management and reliable communication between services.

• Develop and optimise data models and queries in PostgreSQL.

• Work with BigQuery and data-related services when required.

• Contribute to CI/CD pipelines and deployment processes using GitHub Actions, Docker and Kubernetes.

• Participate in the deployment and operation of applications on GCP, including services such as Compute Engine, Pub/Sub and Cloud Run.

• Maintain and improve application monitoring and error tracking through Datadog and Sentry.

• Contribute to dashboards, alerts, performance indicators and production issue investigations.

• Write clean, tested and maintainable code and actively participate in code reviews.

• Collaborate with Product, Data, Infrastructure and Engineering teams to deliver pragmatic technical solutions aligned with business priorities.

Technical Environment

Backend: Python, FastAPI, Django, Flask
APIs: REST, GraphQL
Databases: PostgreSQL, BigQuery
Cloud: GCP, Compute Engine, Pub/Sub, Cloud Run
Observability: Datadog, Sentry
CI/CD and Operations: GitHub Actions, Docker, Kubernetes
Architecture: Microservices, distributed systems, scalable SaaS platforms

Candidate Profile

• At least 4 years of professional experience in backend development, with strong hands-on experience in Python.

• Solid knowledge of at least one Python backend framework such as FastAPI, Django or Flask.

• Previous professional experience within a startup or scale-up environment is mandatory.

• Experience developing and maintaining SaaS products, marketplaces or complex web applications.

• Good understanding of REST APIs and backend application architecture.

• Initial experience with microservices, distributed systems or asynchronous architectures.

• Good knowledge of PostgreSQL, including data modelling, query optimisation and database reliability.

• Familiarity with backend performance topics such as API latency, database optimisation, caching, traffic management and monitoring.

• Experience with cloud environments, ideally GCP.

• Hands-on experience with Docker and CI/CD pipelines.

• Knowledge of Kubernetes, BigQuery, Pub/Sub or Cloud Run would be a strong advantage.

• Strong software quality mindset, including testing, code reviews, maintainability and production reliability.

• Ability to work autonomously while collaborating effectively with more experienced engineers.

• Pragmatic and product-oriented mindset, with the ability to operate in a fast-paced environment.

• Fluent professional English is mandatory, as the consultant will work within an international and distributed team.