Aitor Nain Mendoza Vallejo · NainDev

Full stack software architect: reliable backend and verifiable AI.

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Complete product in Python and .NET, with AI under human review and deterministic product conformance, today applied to 3D models in DSE.

I take on part-time, remote projects for companies in any country.

Python · C# · FastAPI · .NET · PostgreSQL · SQL Server · Vue 3 · MCP

Verifiable

Portfolio

Selected work

2 selected projects

  1. 01Public demo available

    Policy Operations API

    Result
    With synthetic data, the public API lets you walk a policy through Draft, Active and Cancelled and trigger a controlled concurrency conflict.
    Problem
    A policy's life cycle demands isolating each organisation's data, auditing every change and resolving concurrent edits without losing any.
    Approach
    A .NET 10 API with JWT roles, optimistic concurrency (rowversion, ETag and If-Match), ProblemDetails errors and CI against a real SQL Server.
    • C#
    • .NET 10
    • EF Core
    • SQL Server
    • Azure

    Test API Review Code How it is built

  2. 02Active public demo

    .NET Modernization Harness (YARP & Shadow Runner)

    Result
    The demo shows transparent routing between the monolith and .NET 10 microservices, and the audit of every difference it detects.
    Problem
    A legacy .NET monolith is not rewritten in one go, and every partial migration risks the behaviour that works in production today.
    Approach
    Strangler Fig with a YARP reverse proxy and a Shadow Runner: the new service runs in parallel and its responses are compared semantically with the monolith's.
    • C#
    • .NET 10
    • YARP
    • Clean Architecture
    • xUnit

    Try the demo Review Code How it is built

How can I help you

Software engineering and architecture

15 services

I design robust, scalable architectures with an infrastructure-agnostic approach, prioritizing reliable data and immutability.

Deterministic product conformance

Multi-domain architecture that validates every product against versioned specifications. Its first product is DSE, for 3D models.

  • Versioned profiles per domain (glTF/GLB first)
  • Topological and Geometric Validation
  • Reproducible verdicts and repair under contract
Learn more →

Generative AI & Agent Integration

Robust agentic ecosystems for integrating AI models into corporate workflows.

  • Cross-cutting agent integration
  • Trustworthy AI and determinism
  • Human-in-the-loop flows
Learn more →

Critical backend (Python and .NET)

Mission-critical systems where data consistency is non-negotiable, on PostgreSQL and SQL Server.

  • Clean Architecture and layered architecture
  • Incremental .NET Framework modernization
  • Concurrency control (versions and ETag)
Learn more →

Technologies

Tech stack

Languages, tools, and platforms I use to build robust architectures.

Languages
Python IconPythonC# IconC#TypeScript IconTypeScriptJavaScript IconJavaScript
Backend
FastAPI IconFastAPIPydantic iconPydantic.NET Icon.NET
Frontend
Vue 3 iconVue 3Tailwind CSS iconTailwind CSSAstro iconAstroThree.js IconThree.js
Data
PostgreSQL iconPostgreSQLSQL Server IconSQL Server
AI & DevOps
MCP iconMCPDocker IconDockerGitHub Actions iconGitHub ActionsAzure iconAzureLinux IconLinux
Tools
Git IconGitGitHub IconGitHubVS Code IconVS Code

Portfolio

Projects and demos

16 projects

I state the real status of each project. Private ones are described by architecture and stack only, with no names or client data.

See all projects and demos →

Products

Contrast3D x NainDev: design and software, from idea to production

DSE · Deterministic conformance

Validates a product against versioned profiles and issues a reproducible verdict. Its first domain is glTF/GLB 3D models.

datumstatutum.com ↗

Contrast Viewer · 3D viewer for the web

A web component that shows 3D models with exploded views and points of interest, ready to embed in a page.

viewer.contrast3dhub.com ↗

Contrast Hub · Private platform

Custom CRM and calculations, in production with a real team. It is private and has no public demo.

Contrast3D
NainDev

NainDev collaborates with Contrast3D, a studio for creative direction, CGI and real-time 3D. Each handles its own part so a product looks good and works reliably.

Creative direction, CGI and motion, real-time 3D and visual product design.

Backend in .NET and Python, deterministic validation and critical-system audits.

Open source

Open ecosystem

Templates, standards and tools I use across all my projects.

How I work

How I organize a small job

First, I clarify what needs to be solved and what is out of scope. Then, I divide the work into changes that can be tested and reviewed.

  1. Understanding the Task

    Objective, context, constraints, and expected outcome.

  2. Preparing for the Change

    I review the affected code and choose the simplest solution that fits.

  3. Develop and Test

    I implement the change and test the important cases.

  4. Deliver

    I explain what was modified, how it was tested, and what remains pending.

Want to see how I apply this methodology at scale?

I documented how we solved the vendor lock-in and scalability problem using Clean Architecture and C#.

Read the technical article

About Me

Software Architect & Backend Specialist

I am Aitor Nain Mendoza Vallejo, also known as Aitor Mendoza and NainDev. I work as CTO at Contrast3D x NainDev, the collaboration with Contrast3D, where I design a deterministic, multi-domain conformance architecture with an Open Core model: designed to validate products from any sector against explicit, versioned specifications, with reproducible verdicts and a 'Trustworthy AI' approach. Its first domain is AI-generated 3D assets.

In parallel, I work full-time in the enterprise sector as a developer and maintainer of critical .NET (C# and SQL Server) systems. My focus combines the rigor and scalability of the corporate world with the cutting edge of Human-in-the-loop and agentic flow integrations.

Real experienceDaily work with .NET and SQL Server.

Reviewable codeThe projects and demos are linked.

Clear scopePart-time, remote projects, with the scope agreed on the first call.

Interactive terminal

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Contact

Is your backend not scaling or is your AI unpredictable?

Technical debt and bottlenecks cost you speed. Write to me, and let's design a robust architecture plan so your team can move forward without fear.

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