Open to opportunities · Adamantina, SP, Brazil

Claudio Matheus

.NET Backend Developer

I build REST APIs, microservices and business systems with C#, ASP.NET Core, Entity Framework Core and SQL Server, with a layered architecture and automated tests.

See projects Résumé (PDF, Portuguese) 
var builder = WebApplication.CreateBuilder(args);

builder.Services.AddDbContext<AppDbContext>(o =>
    o.UseSqlServer(builder.Configuration
        .GetConnectionString("Default")));
builder.Services
    .AddScoped<IPaymentService, PaymentService>();

var app = builder.Build();

app.MapPost("/api/payments", async (
    CreatePaymentDto dto,
    [FromHeader(Name = "Idempotency-Key")] string key,
    IPaymentService svc) =>
{
    var payment = await svc.CreateAsync(dto, key);
    return Results.Created(
        $"/api/payments/{payment.Id}", payment);
});

app.Run();

About

Backend code built to last

I'm a .NET backend developer with almost 2 years of professional experience in C#, SQL Server and system integration. At work I build and maintain data integrations across Oracle, SQL Server and MySQL, tune T-SQL queries and stored procedures, and troubleshoot production failures.

In my own projects I build REST APIs with ASP.NET Core and Entity Framework Core in layers (API, Application, Domain, Infrastructure), with automated tests, CI, and authentication, idempotency and structured logging from day one. I created AuditLogCM, an open source library published on NuGet, and I'm in the 8th semester of a Computer Science degree.

  • Layered architectureIsolated domain, dependencies pointing inward
  • MicroservicesHTTP with retry/circuit breaker and messaging with RabbitMQ
  • DataSQL Server, EF Core, Dapper, stored procedures, views and triggers
  • QualityTests with xUnit, Moq and NSubstitute; logging with Serilog

Experience

Where I work

~2 yearsof professional experience with C#, .NET and SQL Server
3 h → 53 minETL pipeline processing time (≈70% faster)
1,300+AuditLogCM downloads on NuGet

Junior Integration and Systems Analyst · SmartBreeder

Jun 2026 – present
  • Root cause analysis of production integration failures, with log and alert monitoring.
  • SQL Server queries and extractions to investigate incidents and validate data quality.
  • Implementing and versioning per-customer business rules and technical onboarding of new customers.

Junior ETL Developer · SmartBreeder

May 2025 – May 2026
  • Built and maintained C#/.NET applications integrating customer systems (Oracle, SQL Server, MySQL) with internal platforms.
  • Cut ETL pipeline processing time from about 3 hours to 53 minutes with concurrency control in Python/Apache Airflow.
  • Optimized T-SQL queries and stored procedures and added logging and exception handling to the integrations.
  • Set up end-to-end integrations: endpoints, mappings, user acceptance, testing and documentation.

ETL Development Intern · SmartBreeder

Nov 2024 – Apr 2025
  • Integrations in C#/.NET and Python, T-SQL queries and Apache Airflow pipeline maintenance. Hired full time as Junior ETL Developer.

B.Sc. in Computer Science · UNIFAI

2023 – in progress
  • Centro Universitário de Adamantina, currently in the 8th semester.

Stack

Technologies I use every day

Backend

  • C#
  • .NET 8 / 9
  • ASP.NET Core
  • REST APIs
  • Entity Framework Core
  • Dapper
  • LINQ
  • MediatR
  • ASP.NET Identity
  • JWT

Data and integration

  • SQL Server
  • T-SQL
  • Stored Procedures
  • Oracle
  • MySQL
  • Python
  • Apache Airflow
  • RabbitMQ

Architecture and quality

  • Clean Architecture
  • SOLID
  • Repository Pattern
  • xUnit
  • Moq
  • NSubstitute
  • Serilog

DevOps and tooling

  • Git
  • GitHub Actions
  • GitLab
  • Docker
  • Azure (VMs)
  • NuGet
  • Angular
  • React

Projects

Featured projects

A selection of my repositories. Technical documentation is written in Portuguese; the code speaks C#.

NuGet library Docs

AuditLogCM

Hooks into EF Core's SaveChanges and records a full audit trail: who changed what, when, and the previous value. Plugs into any ASP.NET Core app with one line of configuration. 1,300+ downloads on NuGet.

  • .NET
  • EF Core
  • NuGet
Docs NuGet Code
Monitoring Docs

DataPulseCM

Centralized monitoring for ETL jobs: standardized execution logging, a REST API for queries, success and failure statistics and step-by-step tracing.

  • ASP.NET Core 9
  • SQL Server
  • Clean Architecture
Docs Code
Payment gateway Docs

CMPay

Payments API (Pix, credit and debit) with idempotent creation, API key authentication, refunds and cancellations, structured logging and unit tests.

  • .NET 9
  • EF Core
  • Serilog
  • xUnit
Docs Code
Microservices

NotaFiscalCM

Invoice issuing with inventory updates across two microservices. They talk over HTTP with retry and circuit breaker, and the inventory update is idempotent per invoice.

  • .NET 9
  • Angular 19
  • Resilience
Code
Full stack

CMWallet

Personal finance app with accounts, categories, transactions and goals. Layered REST API with health checks and an Angular SPA with SSR and light/dark themes.

  • .NET 9
  • Angular
  • SQL Server
  • NSubstitute
Code
Microservices Docs

ECommerceCM

E-commerce split into product, cart, coupon, order and payment services, with IdentityServer and JWT authentication and RabbitMQ messaging.

  • ASP.NET Core
  • RabbitMQ
  • IdentityServer
  • Docker
Docs Code

More projects

  • FinanceTrackerCM Finance management with Clean Architecture, CQRS via MediatR, JWT with refresh tokens and auditing via AuditLogCM.
  • LinkCM URL shortener with click counting and expiration. ASP.NET Core, React and Docker Compose.
  • AuthCM Authentication and authorization with ASP.NET Core Identity, JWT and Angular.
  • Work Session Tracker Track and analyze work sessions. ASP.NET Core 8 and React 19.
  • ObservaNet Observability dashboard and centralized logging for ASP.NET Core apps.
  • ServerDisplayCM Physical display (ESP32) showing PC hardware metrics, fed by a .NET agent.

See all repositories on GitHub

Articles

From the blog

Write-ups of the technical decisions behind my projects (in Portuguese).

CMPay · ASP.NET Core · EF Core · PT

How I implemented idempotency in CMPay

An Idempotency-Key header, a payload hash and a unique database index to close the race between concurrent requests.

Read article AuditLogCM · EF Core · NuGet · PT

Automatic auditing with an EF Core interceptor

Capturing who changed what without scattering audit code everywhere, and the catch with IDENTITY keys.

Read article

Contact

Let's talk

I'm open to .NET backend roles. Email or LinkedIn are the fastest ways to reach me.

claudiomatheus055@gmail.com LinkedIn GitHub Résumé (PDF)