Madrid, Spain | Backend Developer & Business Software Consultant
I specialize in APIs, business logic, and databases. This portfolio houses my personal projects and technical demos, reflecting my expertise and continuous learning.
My primary objective is to help companies, startups, and professionals build, scale, and refactor business software over the weekends, ensuring maximum architectural quality, robust persistence, and highly maintainable code.
- REST API Development & Architecture (.NET 10 & Python 3.12): Design by Contract, JWT, observability, advanced concurrency control (ETag,
rowversion), and secure versioning. - Clean Architecture & Domain-Driven Design (DDD): Legacy code refactoring, technical debt elimination, and strict separation between domain and infrastructure layers (EF Core 10, Dapper, SQLAlchemy).
- Database Optimization (SQL Server & SQLite): High-performance T-SQL queries, indexing, stored procedures, auditing, and multitenant isolation.
- Cloud Integrations & Asynchronous processing (Cost-Efficient): Implementation of unattended microservices (Workers), message queues (RabbitMQ / CloudAMQP), and optimized deployments on Azure App Service, Streamlit Cloud, and GitHub Pages.
All my developments are built on the premise of verifiable evidence. No complex downloads or local configurations are required; you can test them in real-time in the cloud or review their architecture directly:
| Project / Domain | Tech Stack | Status & Evidence | Quick Access |
|---|---|---|---|
| Financial Policy Operations API | .NET 10 EF Core 10 SQL Server Clean Architecture Azure |
Live HTTPS Demo. Manages the Draft -> Active -> Cancelled lifecycle, organizational isolation, and ETag concurrency control. |
Test API on Azure View Repository |
| Cloud Notifications Service | .NET 10 MassTransit RabbitMQ (CloudAMQP) MailKit |
Live Simulation. Decoupled microservice connecting to a RabbitMQ cluster with <350ms processing and HTML email dispatching. | Open Web Demo View Repository |
| TAI Civil Service Exam System | .NET 10 Dapper T-SQL Procedures Responsive SPA |
Interactive Demo. Real study platform with official INAP exam timer, official grading (+1/-0.33), and localStorage analytics. |
Test Live App View Repository |
| NainDev Driving School Management | Python 3.12 Pydantic v2 Streamlit SQLAlchemy SQLite |
24/7 Web Demo. Accounting and operational dashboard. Logs classes, calculates balances, and issues official downloadable PDF invoices. | Test Cloud Demo View Repository |
| Pong Arcade Canvas | HTML5 Vanilla CSS JavaScript Canvas API |
Browser Game. Dynamic prototype with real-time physics, multiple AI levels, and a local two-player mode. | Play in Browser View Code |
┌───────────────────────────────┐
│ APIs & Web Applications │ ── ASP.NET Core 10 | Python FastAPI / Streamlit | Vanilla Web
└───────────────┬───────────────┘
▼
┌───────────────────────────────┐
│ Domain & Business Layer │ ── Clean Architecture | DDD | Pydantic v2 | Contract Pattern
└───────────────┬───────────────┘
▼
┌───────────────────────────────┐
│ Persistence & Asynchrony │ ── SQL Server (T-SQL) | SQLite | EF Core 10 | Dapper | RabbitMQ
└───────────────────────────────┘
If you are looking for a reliable developer to drive a critical feature, optimize heavy SQL Server queries, or build the relational brain of your product from scratch with clean and maintainable code, write to me and we'll review the scope in a quick 30-minute brief:
- Interactive Portfolio: www.naindev.com
- Email: contact@naindev.com
- LinkedIn: Aitor Nain Mendoza Vallejo