About

I’m Jonathas Costa, a software engineer based in Porto, Portugal. I call myself a software crafter because the part of the job I care about most is the craft: code that is clear to the next person, systems that keep working when the traffic doubles, and tests that let a team change things without fear.

What I work on

Most of my career has been on the back end, with .NET and SQL Server, on Azure and AWS. I have built APIs for payments and insurance, moved legacy applications to current versions of .NET, automated builds and releases, and set up the monitoring that tells a team something is wrong before its users do. More recently I have been building AI agents: assistants that answer questions from a company’s own data and tools.

I have worked in fashion e-commerce, games, scientific research, credit cards and payments, insurance, transportation, veterinary pharmaceuticals, financial analytics and mining, as an engineer, a lead and an architect. The full list, with what I did at each company, is on my journey; the latest roles are:

Ardanis / Plain Concepts, Senior Software Engineer (2025 – present)
Proxify / Univet, Senior Software Engineer (2024 – 2025)
YLD / NewDay, Senior Software Engineer (2024)
22 cans, Senior Software Engineer (2023 – 2024)

What I build on my own

Outside client work I build small products end to end, from the first sketch to the store listing:

Original Table Games: Four original casino table games: the player rolls the dice and the dealer deals the cards. Three are ready to play with virtual chips, their math proven exactly and by simulation.
Salary Converter: Converts a salary between hourly, daily, weekly, monthly and yearly pay in BRL, USD, EUR and GBP, with the Central Bank of Brazil’s exchange rates and shareable links.
Arrows: A calm, clever puzzle: tap the arrows out, one by one, and clear the board. Endless levels, a daily challenge and a league, now on the App Store and on the web.
Decanta: A calm water sort puzzle: pour the colors until every tube holds one. Endless levels, a daily puzzle and a league, on the web now and soon on the iPhone.
Moat: A calm castle logic puzzle: one castle per row, column and realm, none touching. Endless levels, a daily challenge and a league, on the web now and soon on the iPhone.
Drift: A neon arcade space shooter for one thumb: waves of enemies, bosses and power-ups worth the risk. Endless runs and a daily run, on the web now and soon on the iPhone.
Sudoku: A Sudoku with three levels, notes, undo and hints. It saves your game as you play and works offline.

What I write about

The articles on this site come from that work: upgrading .NET, SQL Server features worth knowing, observability with OpenTelemetry and Grafana, .NET on AWS Lambda, and how the puzzle generators behind my games work. Most of them show code that runs, with the output it produced.

Get in touch

If you want to talk about a project, a role or something you read here, write tojonathas.costa@gmail.com, or find me on LinkedIn andGitHub.