Freelancer profile translated to English.

Description

I fix, stabilize, and build Python backends in production: REST API, FastAPI, PostgreSQL, and VPS deployments.

I primarily work on existing backend projects to resolve blocking bugs, reduce technical debt, secure flows, and ensure business logic reliability before production release. My goal is simple: to make a backend stable, readable, and sustainably maintainable.

I have designed and maintained several backend APIs focused on automation, webhooks, and asynchronous processing, with a particular focus on security (JWT, HMAC, anti-replay protections), data migrations, and automated testing.

My approach is pragmatic and results-oriented: quickly analyze the existing system, identify critical points, and deliver clean, documented, and maintainable fixes.

I can design a complete REST API (FastAPI, PostgreSQL, SQLAlchemy, Alembic, OpenAPI) or provide support for an existing backend to get it back on track, improve its stability, and prepare it for production.

Industry field of expertise

Languages

French
Native or bilingual
English
Fluent

Workplace preferences

Remote only

Primarily works remotely

NDA THEOBROMA
On Malt
Targeted Corrective Maintenance – Python/Django Application
SOFTWARE PUBLISHING
January 2026 - January 2026
Targeted corrective maintenance on a Python/Django backend application, involving intervention on an existing production database.

Key Contributions

- Analysis and diagnosis of backend malfunctions on an existing Django application
- Targeted correction of application errors and improvement of API stability
- Functional validation of fixes and runtime checks
- Preparation of the final deliverable and support for project closure

Results

- Backend issues identified and addressed within a defined contractual scope
- Application returned to a state compliant with the planned maintenance scope
- Structured and documented final delivery
Python Django FastAPI REST API Application Maintenance
LELEU Stéphane
Backend Developer – Webhook Management Platform (Showcase Project)
SOFTWARE PUBLISHING
December 2025 - Today (6 months)
Épinay-sur-Orge, France
Design and development of a backend platform for webhook management focused on reliability, security, and auditability.

Implementation of authenticated webhook endpoints with HMAC SHA-256 validation, anti-replay protection (timestamp and nonce), and secure ingestion of external payloads.

Implementation of asynchronous event processing using Celery and Redis, with routing to multiple destinations, automatic retry system with exponential backoff, and detailed history of delivery attempts.

Modular backend architecture (API, services, repositories), PostgreSQL database with Alembic migrations, JWT authentication, automated testing, and observability endpoints for flow monitoring and diagnostics.
FastAPI REST API Webhooks PostgreSQL Automated Testing
LELEU Stéphane
Backend Developer – Invoicing & Automation Tool
SOFTWARE PUBLISHING
December 2025 - Today (6 months)
Épinay-sur-Orge, France
Design and development of a complete backend for management and invoicing for freelancers and small businesses.

Implementation of a REST API (FastAPI) covering client, product, quote, and invoice management, with automatic numbering, locking after sending, quote-to-invoice conversion, payment management (draft, sent, partial, paid, canceled statuses), and activity log.

Modular API/services/repositories architecture, SQLite database with Alembic migrations, reliable HT/VAT/TTC calculations with controlled rounding, JWT authentication, single-tenant company profile, and automated testing (pytest/httpx). OpenAPI documentation included.
FastAPI SQLAlchemy REST API Alembic Software Architecture