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Gael TuczapskiGT

Gael Tuczapski

.NET Backend Developer | LLM & AI Integration

€300/day
Aix-en-Provence, FR
3-7 years

Average response time: 1 hour

Freelancer profile translated to English.
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About Gael

.NET backend developer, I design business applications and integrate LLMs properly: structured outputs, anti-hallucination guardrails, multi-provider, so that it holds up in production, not just in POC.

Concretely, I solve the problem end-to-end: a .NET backend that handles the load, an LLM component that doesn't drift, and the deployment to production that goes with it.

My approach to AI can be summed up in one sentence: the LLM suggests, the code disposes. Language to the model, never business invariants.
Two examples designed alone: SignalLab-extractor, a pipeline that extracts structured data (schema-constrained JSON) from video content via LLM (Claude, multi-provider Ollama / OpenAI-compatible endpoints, Message Batches API), then verifies it in backtest. And Polaris, a business DMS in a regulated environment (.NET 10, Blazor Server, EF Core 10, tamper-proof audit by SHA-256 chaining, RBAC).

In the field: three years of work-study at Capgemini Engineering at the CEA Marcoule nuclear center, where I single-handedly led the redesign of a business application with ~5,000 users (.NET 8, Blazor Server, Clean Architecture, CQRS, Active Directory SSO). And a team SaaS, Buy&Rent, where I built the data services (collection, processing, and storage from 8 public sources) on a .NET 10 microservices / Kubernetes architecture.

What I'm good at:
- Integrating LLMs into business apps (structured outputs, anti-hallucination, multi-provider)
- Robust .NET backend: ASP.NET Core, EF Core, PostgreSQL / SQL Server, microservices
- Clean and testable architecture: Clean Architecture, CQRS
- From code to deployment: Docker, Kubernetes (K3s), CI/CD GitOps

IMT Mines Alès Engineer. A .NET application to upgrade, an LLM to integrate without it hallucinating, a product to build? Let's talk about it.
  • French

    Native or bilingual

  • English

    Native or bilingual

Remote only
Primarily works remotely

Experience

  • Capgemini Engineering,
    Software Engineer (CEA Marcoule)
    ENERGY AND UTILITIES
    July 2023 - Today (3 years)
    Bagnols-sur-Cèze, France
    TMA team for the CEA Marcoule nuclear center (~5,000 people). Senior IC in a team of 5 engineers. Regulated environment, security clearance.
    • PREST-O, corporate catering application (~5,000 daily users): complete redesign to .NET 8 + Blazor Server, Clean Architecture + CQRS (MediatR), Active Directory SSO. Delivered autonomously in ~3 months
    • Measurement of SignalR server cost vs. real update volume, replaced by a lighter polling service to simplify the architecture and reduce load
    • .NET 10 modernization audit of ~20 applications across 5 stacks; feasibility reports cost/risk presented to decision-makers
    • Containerization of a legacy .NET application (Docker + Kubernetes); resolution of a network issue LDAP/AD related to container isolation
    • Intervention on ~30 applications and 5 .NET stacks in a regulated environment, adaptation to 3 successive technical managers over 3 years
    .NET C# Blazor Docker React.js
  • BuyAndRent
    Co-founder & Lead Backend
    REAL ESTATE
    February 2024 - Today (2 years and 5 months)
    France
    B2C SaaS for rental investment analysis (buyandrent.fr). Team of 4 engineers (2 backend), led in parallel with my work-study. I designed and deployed the backend architecture and wrote the core business logic of the product:

    • LLM integration (Mistral) for regulatory monitoring and content generation, made reliable for production use: structured outputs, guardrails, without entrusting business invariants to the model.
    • Data services (DataCollector, DataProcessor, DataStorage): collection, processing, and storage from 8 public sources (INSEE, DVF, DPE, risks, schools) with caching and refresh strategies.
    • Profitability calculation engine over 25 years: cash flow projections, multi-regime tax scenarios, scoring.
    • .NET 10 / ASP.NET Core microservices architecture on Kubernetes (K3s), event-driven via RabbitMQ/MassTransit, PostgreSQL 16 + PostGIS, Keycloak (OIDC), RGPD compliant by design.
    • End-to-end observability (Serilog/ELK, Prometheus, Grafana) and full CI/CD (GitHub Actions, ArgoCD/GitOps, vulnerability scanning).

    A product taken from idea to production, on a modern .NET stack mastered from code to deployment.
    Kubernetes .NET C# RabbitMQ ASP.NET Core

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Education

  • Engineering Degree
    IMT Mines Alès
    2026
    Diplôme d'Ingénieur
  • Bachelor's Degree
    Aix-Marseille University
    2023
    Licence

Skill set

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