Since 2004Curitiba, Brazil · Sunday, November 8, 2026Português

Developer Journal

Listings, notes and work history of Carlos, senior software engineer. Filed from Curitiba, Brazil.

For hire · Senior software engineer

Legacy systems connected to modern software, and backends your team runs on its own.

22 years in software, 13 of them building ERPs. Remote work, and every project ends with the code in your repository, tests passing, and documentation your team can use.

> describe your project> see selected work

Services offered

3 listings

ERP integration & SaaS backends

Integration of ERPs such as SAP, Microsoft Dynamics and custom systems with the software around them: interfaces, sync jobs, retries, monitoring and a runbook that explains them.

Backends for products that serve many customers from one codebase: tenant isolation, queues, and LLM features such as provider routing, retrieval and tracing. Built on C# and .NET, on Cloudflare Workers and TypeScript, or on Python.

You get: design, production code, tests, CI/CD, monitoring, runbook

Web & custom software

Improvements to existing websites and web apps: speed, accessibility, search visibility, new features, bug fixes, and moving old stacks to current ones. Front ends in Vue.js, React and Astro; back ends in .NET, TypeScript or Python.

Also custom software in general: internal tools, APIs, automations, data jobs and desktop apps.

You get: working code in your repository, tests, deploy, documentation

Technical audit

One to two weeks, fixed price. A review of your code and infrastructure, with a report on what is fragile, what is slow, what is unsafe and what to fix first.

Useful before a rewrite, a migration, or taking over a codebase.

You get: written report, prioritized fixes, migration plan, one-hour walkthrough

How it works

5 steps
  1. Discovery and analysis. A close look at the problem, at what the systems do today and at what must not break, before any estimate.
  2. Written scope. Goal, deliverables, what is out of scope, milestones and price. Changes are estimated and approved before work starts.
  3. First working slice in week one. A thin end-to-end path in a test environment, so misunderstandings surface early.
  4. Weekly demo and report. What shipped, what is next, risks, and the decisions that need your call.
  5. Handover and warranty. A recorded walkthrough, a clean transfer of access, and 14 to 30 days of fixes for the delivered scope.

Every project delivers

  • Code in your repository, in reviewable pull requests
  • Automated tests and a CI pipeline
  • README: a new developer runs it in 15 minutes
  • Architecture decision records
  • Runbook: deploy, monitor, roll back
  • Recorded handover and a final report

Selected work

6 listings

SAP S/4HANA integration program

Client work

One reliable path from the company’s systems to SAP. .NET middleware built and maintained to connect the company’s systems to SAP S/4HANA, with a portal for operators to follow every integration and shared libraries reused by other projects.

Stack: C#, ASP.NET Core, SQL Server, SAP .NET Connector, Vue.js

Tax, production and warehouse systems

Client work

Bloco K, RECOF and the legacy warehouse. A tax and production data platform that feeds the tax and customs platform every day, and the move of legacy warehouse interfaces to C#.

Stack: C#, .NET, SQL Server, Oracle, Hangfire

ERP for Brazilian tax and accounting

MPS Informática · 2008–2021

13 years on one ERP, from programmer to systems analyst. Finance, billing, inventory, purchasing, accounting and tax modules. On the SPED project from the start, plus electronic invoices (NF-e) for goods and services and CNAB bank files, with each change taken from requirements and specifications through database modeling, testing, rollout and production support.

Stack: C#, .NET Framework, Centura (SQL Windows), SQL Server, Sybase

Market analysis terminal

Own product · Continuous development

Nebula. A desktop terminal for technical analysis that runs natively on Mac, Windows and Linux. Indicators are computed in Rust and tested against known values; a hidden Markov model detects the market regime, and a Monte Carlo simulation draws the risk cone. It also shows studies from a separate technical analysis engine. Historical data works today; live streaming is next.

Stack: Rust, Tauri, DuckDB, Parquet, SolidJS, KLineChart

AI framework

Own product · Continuous development

AI for people and for systems. A framework for assistants that talk to customers and for AI integrations with other systems, each answering from its own knowledge base through retrieval-augmented generation (RAG) over pgvector. The multi-agent orchestration is written from scratch: requests are routed across model tiers on Azure OpenAI, Gemini and Llama, and every step is traced in LangFuse.

Stack: TypeScript, Cloudflare Workers, Durable Objects, Hono, Supabase, pgvector, Drizzle ORM

Credential rotation

Own product · Continuous development

Secrets Rotator. Keys, tokens and passwords need to be replaced regularly: they expire, they leak, and security policies require it. Done by hand, rotation is easy to forget and easy to get wrong, and a system left with the old key stops working. This application makes rotation routine: one place to rotate each credential and update every system that uses it, on top of the cloud secret manager already in place.

Stack: Python, Django, Celery, Azure Key Vault

Inventory

Tools on the shelf
ERP, integration
SAP S/4 (integration layer, production planning), Microsoft Dynamics, custom ERPs; billing, inventory, purchasing, accounting; NF-e, SPED, CNAB
Languages
C# (.NET), TypeScript, Python, SQL
Backend
.NET, REST API design, dependency injection, Hono, Django, Celery, Durable Objects, Drizzle ORM
Data
SQL Server, Sybase, PostgreSQL, Supabase, pgvector; data modeling, execution-plan analysis, query tuning
AI
LLM routing across providers, retrieval-augmented generation, multi-agent design, LangChain.js, LangFuse
Cloud, CI
Cloudflare Workers, Azure (OpenAI, Key Vault), Oracle Cloud, GitHub Actions
Security
Secret management and rotation, FIDO2 and hardware keys, Cloudflare Zero Trust
Process
Conventional Commits, architecture decision records, enterprise change management (CAB, ITIL)
Spoken
Portuguese (native), English (professional working), Spanish (elementary)

Diary

Newest first
  1. 2023-08 → nowOnline Systems · Sumitomo Rubber do Brasil

    Senior .NET C# developer

    Contract role via Online Systems, on assignment at Sumitomo Rubber do Brasil in Fazenda Rio Grande, Paraná. Systems integration, functional analysis and architecture across industrial, tax, quality and warehouse systems. Since 2025, the SAP S/4HANA program: the .NET middleware, its queue, the partner integrations and the operations portal.

  2. 2011-01 → 2021-04MPS Informática

    Systems analyst

    ERP modules for finance, billing, inventory, purchasing, accounting and tax, including bank files (CNAB) and electronic invoices for products and services. Part of the SPED and NF-e projects from the start, as analyst and programmer in every phase: requirements, specifications, database modeling, development, testing, rollout and support.

  3. 2008-01 → 2010-12MPS Informática

    Programmer

    C# on .NET Framework and Centura (SQL Windows) over Sybase and SQL Server. Database modeling, query writing, execution-plan analysis and tuning.

  4. 2006-08 → 2008-01Curitiba City Council

    Intern

    Legislative proposals system in Java 5 that automates how councillors draft bills. Shell and SVN scripts for test, staging and release automation.

  5. 2004-07 → 2006-08UFPR

    Research assistant

    CNPq scholar in the Physics and Meteorology lab: FORTRAN 77, C++ and Bash for rain, wind and temperature analysis, plus the lab's Linux servers and network. Before that, an internship on Mouse Eye, an accessibility app that moves the mouse by tracking the eyes (C++, X.org).

  6. 2003 → 2010UFPR

    B.Sc. Computer Science

    Federal University of Paraná. Thesis on the derandomization of BPP algorithms. Certificate: Understanding and Documenting REST / RESTful APIs.

  7. OngoingWriting

    Article series

    Articles that connect computer science theory to the technology used at work, starting from revisiting that thesis, in Portuguese and English.

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